Theresa May is to raise concerns with Donald Trump after evidence from the Manchester Arena bombing was apparently leaked to US media.
UK officials were "furious" when photos appearing to show debris from the attack appeared in the New York Times.
Monday night's attack at Manchester Arena killed 22 people - including children - and injured 64.
Eight men are now in custody following the attack, carried out by suicide bomber Salman Abedi.
The prime minister is expected to raise the issue of the leak with the US president when they meet at a Nato summit later.
Details about Abedi's identity had already emerged in the US media less than 24 hours after the explosion and against the UK's wishes.
Home Secretary Amber Rudd said she was "irritated" by the disclosure of Abedi's identity and had warned Washington "it should not happen again".
However, the pictures of debris - which appear to show bloodstained fragments from the bomb and the backpack used to conceal it - were subsequently leaked to the New York Times, prompting a furious response from within Whitehall and from UK police chiefs.
BBC security correspondent Gordon Corera says UK officials believe that US law enforcement rather than the White House is the likely culprit for the leaks.
Further two arrests
The meeting between Mrs May and Mr Trump, at a Nato summit in Brussels, will take place as British police continue to investigate an alleged "network" linked to Abedi.
Early on Thursday morning, detectives carried out a controlled explosion as they searched a property in the Moss Side area of Manchester.
Two men were also arrested following a search of an address in the Withington area of Greater Manchester.
In total, eight men, including Abedi's older brother, and a woman have been arrested in a series of raids across Manchester, Wigan and Nuneaton.
The woman was subsequently released without charge in the early hours of Thursday.
Meanwhile, Abedi's father and a younger brother have been detained by militia in Libya.
A Whitehall source described the second US leak as "on another level", and told the BBC it had caused "disbelief and astonishment" across the British government.
The source said the the issue was "being raised at every relevant level by the British authorities with their US counterparts".
The UK's National Police Chiefs' Council described the "unauthorised disclosure" as a breach of trust which had potentially undermined a "major counter-terrorism investigation".
Counter-terrorism detectives have spoken in the past about how important it sometimes is the names of suspects do not make it into the media.
A delay of around 36 hours, before the public know who they are investigating, can allow them to arrest known associates of the suspect before they know police are looking for them.
Greater Manchester Mayor Andy Burnham said the leaks had worried him "greatly," and he had raised them with the US ambassador.
Mr Burnham told Newsnight a decision had been taken to adopt a "cautious approach" to making information public, "and yet the first reports were coming seemingly out of the United States".
Abedi's identity was first reported in the US - with American TV networks CBS and NBC naming him as the suspect.
In other developments, the government has announced that a minute's silence will be held at 11:00 BST on Thursday in remembrance of those who lost their lives or were affected by the attack.
The Conservatives and Labour are to resume local general election campaigning on Thursday, and national campaigning on Friday.
What's happening with the investigation?
Eight men and one woman have been arrested in the UK since Monday night, including Abedi's older brother Ismail, 23, although the woman has since been released.
Younger brother Hashem, 20, was held by militia in the Libyan capital Tripoli, as was their father.
Speaking on Wednesday afternoon, Greater Manchester Chief Constable Ian Hopkins said: "I think it's very clear that this is a network that we are investigating.
"And as I've said, it continues at a pace. There's extensive investigations going on and activity taking place across Greater Manchester, as we speak."
As part of their investigation, police raided a block of flats near Manchester Piccadilly station in the city centre, requiring them to carry out a controlled explosion and briefly close the railway line.
Police carried out another controlled explosion in the early hours of Thursday morning at an address in the Moss Side area of Manchester.
Anyone with information about the attack can call the anti-terror hotline on 0800 789321.
Source : http://www.bbc.com/news/uk-politics-40040210
UK officials were "furious" when photos appearing to show debris from the attack appeared in the New York Times.
Monday night's attack at Manchester Arena killed 22 people - including children - and injured 64.
Eight men are now in custody following the attack, carried out by suicide bomber Salman Abedi.
The prime minister is expected to raise the issue of the leak with the US president when they meet at a Nato summit later.
Details about Abedi's identity had already emerged in the US media less than 24 hours after the explosion and against the UK's wishes.
Home Secretary Amber Rudd said she was "irritated" by the disclosure of Abedi's identity and had warned Washington "it should not happen again".
However, the pictures of debris - which appear to show bloodstained fragments from the bomb and the backpack used to conceal it - were subsequently leaked to the New York Times, prompting a furious response from within Whitehall and from UK police chiefs.
BBC security correspondent Gordon Corera says UK officials believe that US law enforcement rather than the White House is the likely culprit for the leaks.
Further two arrests
The meeting between Mrs May and Mr Trump, at a Nato summit in Brussels, will take place as British police continue to investigate an alleged "network" linked to Abedi.
Early on Thursday morning, detectives carried out a controlled explosion as they searched a property in the Moss Side area of Manchester.
Two men were also arrested following a search of an address in the Withington area of Greater Manchester.
In total, eight men, including Abedi's older brother, and a woman have been arrested in a series of raids across Manchester, Wigan and Nuneaton.
The woman was subsequently released without charge in the early hours of Thursday.
Meanwhile, Abedi's father and a younger brother have been detained by militia in Libya.
A Whitehall source described the second US leak as "on another level", and told the BBC it had caused "disbelief and astonishment" across the British government.
The source said the the issue was "being raised at every relevant level by the British authorities with their US counterparts".
The UK's National Police Chiefs' Council described the "unauthorised disclosure" as a breach of trust which had potentially undermined a "major counter-terrorism investigation".
Counter-terrorism detectives have spoken in the past about how important it sometimes is the names of suspects do not make it into the media.
A delay of around 36 hours, before the public know who they are investigating, can allow them to arrest known associates of the suspect before they know police are looking for them.
Greater Manchester Mayor Andy Burnham said the leaks had worried him "greatly," and he had raised them with the US ambassador.
Mr Burnham told Newsnight a decision had been taken to adopt a "cautious approach" to making information public, "and yet the first reports were coming seemingly out of the United States".
Abedi's identity was first reported in the US - with American TV networks CBS and NBC naming him as the suspect.
In other developments, the government has announced that a minute's silence will be held at 11:00 BST on Thursday in remembrance of those who lost their lives or were affected by the attack.
The Conservatives and Labour are to resume local general election campaigning on Thursday, and national campaigning on Friday.
What's happening with the investigation?
Eight men and one woman have been arrested in the UK since Monday night, including Abedi's older brother Ismail, 23, although the woman has since been released.
Younger brother Hashem, 20, was held by militia in the Libyan capital Tripoli, as was their father.
Speaking on Wednesday afternoon, Greater Manchester Chief Constable Ian Hopkins said: "I think it's very clear that this is a network that we are investigating.
"And as I've said, it continues at a pace. There's extensive investigations going on and activity taking place across Greater Manchester, as we speak."
As part of their investigation, police raided a block of flats near Manchester Piccadilly station in the city centre, requiring them to carry out a controlled explosion and briefly close the railway line.
Police carried out another controlled explosion in the early hours of Thursday morning at an address in the Moss Side area of Manchester.
Anyone with information about the attack can call the anti-terror hotline on 0800 789321.
Source : http://www.bbc.com/news/uk-politics-40040210
