British police have resumed "working closely" with US authorities on the Manchester bombing investigation after a tense showdown between the allies over leaked intelligence.
Mark Rowley, the UK's most senior counter-terrorism officer, confirmed British chiefs had "received fresh assurances" from their overseas counterparts that they could be trusted with confidential material.
Meanwhile, Home Secretary Amber Rudd said she expected the "critical" assessment of the terror threat - suggesting a fresh attack may be imminent - could remain in place for as little as a few days.
Ms Rudd told BBC1's Question Time: "During this period of 'critical', which we hope will only last for a few days - it could be longer, it will depend on the operation - we've pulled out additional support from the army so we can go about our normal life."
The developments followed a fraught day in which Greater Manchester Police severed intelligence-sharing ties with the US due to evidence being repeatedly passed to journalists without permission.
"While we do not usually comment on information-sharing arrangements with international law enforcement organisations, we want to emphasise that, having received fresh assurances, we are now working closely with our key partners around the world including all those in the Five Eyes intelligence alliance," Mr Rowley said.
Salman Abedi, who was known to security services for his radical views, was said to have been in close contact with family members moments before slaughtering concert-goers on Monday.
A relative of the 22-year-old said he had felt increasing frustration at his treatment in the UK, heightened after a friend was fatally knifed in what he perceived to be a religious hate crime.
She added that the British-born bomber began referring to others in the country as "infidels" who were "unjust to Arabs".
Libyan authorities, who are questioning Abedi's parents and siblings, claimed he made a final phone call to his mother on the eve of the attack, in which he said: "Forgive me."
Music fans were targeted at an Ariana Grande concert in Manchester Arena, where Abedi killed 22 people, including seven children, and injured dozens in the worst terrorist attack on British soil since the July 7 bombing in London in 2005.
As Abedi's route to mass murder continued to be probed:
:: Downing Street announced the Government's emergency Cobra committee will meet in Whitehall on Friday morning to discuss the latest developments in the Manchester inquiry, chaired by the Home Secretary.
:: Eight people remained in custody in connection with the investigation.
:: Officers carried out searches at properties in Manchester, Wigan and Nuneaton. A bomb disposal unit returned to the Wigan address on Thursday night so experts could examine "potentially suspicious items".
:: British investigative efforts remained focused on smashing the potential terror ring which may have assisted Abedi, despite the belief of Libyan authorities that he acted alone.
:: Twenty-three people remained in critical care across eight hospitals. They include five children at the Royal Manchester Children's Hospital.
:: British Transport Police announced that specialist firearms officers are to patrol on trains nationwide for the first time.
:: NHS England warned health organisations to "ensure care is in place should it be needed" as Britain remained on high alert in the run-up to the bank holiday weekend.
With the General Election campaign due to resume on Friday, Jeremy Corbyn signalled his intention to bring the issue of terrorism into the political arena.
The Labour leader is expected to make a veiled attack on the Conservatives for underfunding the police service at a time of heightened threat, while linking Britain's overseas military campaigns with terrorism at home.
At the Nato summit in Brussels, Theresa May confronted Donald Trump with her concerns about security lapses which allowed crucial evidence to be handed to US journalists by his officials.
President Trump vowed to investigate, calling the leaks "deeply troubling" and warning the sources of the security lapse could be prosecuted.
In the years leading up to Monday's attack, it was said Abedi was known to security services, but his risk to the public remained "subject to review" and MI5 considered him a "former subject of interest", a Whitehall source said.
Police hunting the "network" behind his attack said they had made "significant" arrests and seized "very important" items in raids.
Mrs May said the terror threat level remains at critical, meaning another attack is expected imminently.
Emergency services on the night and aftermath of the Manchester attack were criticised by the widower of one victim, who accused them of leaving families in the dark.
Steve Howe, whose wife Alison, 45, died as she was waiting to collect their daughter from the concert, told Channel 4 news: "I gave them all the details, all the information from security in the arena, no-one has rang us... I was so frustrated."