Jeremy Corbyn has "been on a journey" since his opposition to Nato and now accepts Labour support for the military alliance, shadow foreign secretary Emily Thornberry has said.
The Labour leader, who has said he would not "automatically" send UK troops to support a Nato member which came under attack and has previously voices his opposition to the alliance, now accepted the will of the party that the transatlantic group was an essential part of the UK's foreign policy, his shadow cabinet ally said.
Ms Thornberry said a Labour government would be prepared to stand up to Donald Trump - but would not rescind the invitation for the US President to make a state visit to the UK later this year.
On BBC One's Andrew Marr Show, Ms Thornberry was challenged about a series of statements on foreign policy made by Mr Corbyn, including his opposition to Nato and comments about the status of the Falkland Islands.
Responding to 2011 footage of Mr Corbyn saying Nato is a "major problem" and a "danger to world peace", Ms Thornberry said: "That's a quote from six years ago and Jeremy has been on a journey, to coin a phrase.
"There have been a number of discussions. It is quite clear that the predominance of opinion within the Labour Party is that we are committed to Nato."
Saying the Labour manifesto would make clear the commitment to Nato, she added: "How would we get our forces off Salisbury Plain at the moment without the assistance of Nato? We don't have enough frigates to be able to move them onto the continent of Europe if necessary if the Russians were to come rolling over the hill."
Asked to repudiate Mr Corbyn's 2011 comments, she said: "I'm not fighting with anybody, I'm telling you that the Labour Party's position is a clear one."
She added that "lots of politicians change their minds".
A government led by Mr Corbyn would only agree to military action on a multilateral basis "which means the UN Security Council", Ms Thornberry said - acknowledging that would potentially give Russia and China a veto over any deployment of British troops.
"It is very difficult," she acknowledged, but said the international agreement for action in Kosovo showed that in some cases there were ways around the Russian security council veto.
On the Falklands, Ms Thornberry said Labour would be prepared to send a taskforce in response to a crisis and there was no question of giving up sovereignty while the islanders wished to remain British.
"There needs to be a future in terms of talking to the neighbours of the Falklands", she said, but "certainly not undermining the sovereignty of the Falkland Islands."
She claimed the Tories were "gung-ho" over the use of force, insisting "you have to look at the alternatives first".
On Mr Trump, Ms Thornberry said: "I would be prepared to stand up to him. I would be prepared to say 'I'm sorry Mr President, but you are wrong about that, we are supposed to be good friends and these values are not our values, you are doing the wrong thing'."
Asked if that meant Mr Trump may decide not to come, Ms Thornberry said: "Well, there we are. I also hear that he doesn't want to share a carriage with Prince Charles because he doesn't agree with Prince Charles on climate change. "
She said the visit would be a "bumpy ride" and accused Theresa May of "fawning" over the US President as she insisted that Labour would focus on human rights in its foreign policy.
Ms Thornberry insisted that would not mean "we are going to boycott China" but there is a "middle way" to follow.
Ms Thornberry was challenged about Mr Corbyn's past after the Sunday Times reported his 1986 arrest at a protest by IRA sympathisers.
"There were negotiations going on behind the scenes and there were people speaking openly and this is something which has been known for 30 years and it has been dragged out at this particular time because there is a General Election on," she said.
"I don't think people should judge Jeremy by trying to talk to people who might be open to a settlement in Northern Ireland."
She added that Mr Corbyn's position was "not having open support for the IRA".