Prime Minister Sir Keir Starmer is set to depart Washington empty-handed on the Ukraine missile issue.
Starmer met with US President Joe Biden at the White House on Friday to discuss Ukraine's request to use Storm Shadow missiles against Russia.
But no announcement on long-range missiles will be made, according to US national security spokesman John Kirby.
The lack of a decision will disappoint those hoping for a breakthrough.
After the talks, Starmer hinted at progress but suggested a final call on Storm Shadow would come later.
"Today was about having a chance to talk not just about a particular step or tactic, but the strategy in relation toUkraine," he said.
The Prime Minister claimed they reached a "strong position" on the matter. A decision may now be delayed until the UN General Assembly later this month.
At the beginning of their meeting in the Blue Room at the White House in Washington DC on Friday, Mr Biden said “I don’t think much about Vladimir Putin” when asked about the Russian President’s threat of war with Nato.
Historically, we've shown the strength of our relationship. We are strategically aligned and we have a common cause on these global issues
Questioned on what they had decided in relation to Ukraine’s potential use of long-range missiles, Sir Keir told reporters: “We had a wide-ranging discussion about strategy in Ukraine, of course, in the Middle East and other parts of the world.
“This wasn’t a meeting about a particular capability. That wasn’t why we got our heads down today.
“It was to allow ourselves the space, which we took, the time, which we took, to have a strategic discussion so that tactical decisions could be seen within the wider strategy.
“It was a really good invitation from the President, we’ve had a very productive (meeting) and we’ve come to a strong position. I’m very pleased that we’ve had these discussions.”
At the beginning of their talks, Sir Keir said the next weeks and months will be “crucial” in Ukraine and said it was “important” the two countries continued to support the eastern European nation in its fight against Russia.
The meeting comes as Ukrainian President Volodymyr Zelensky expressed his frustration at the continued restrictions on the use of Western weaponry against Russian targets.
In a lengthy statement posted on X, Mr Zelensky said after meeting with Foreign Secretary David Lammy and his US counterpart Antony Blinken earlier this week, “there should be no unanswered questions about why Ukraine needs sufficient long-range capabilities”.
At the White House on Friday, Sir Keir told the US President: “Historically, we’ve shown the strength of our relationship.
“We are strategically aligned and we have a common cause on these global issues.”
The PM denied that the need to weaken Mr Putin within months was because of the possibility of a victory for Donald Trump in November’s presidential election.
Questioned on whether Mr Trump’s potential victory was a factor, he told reporters: “No, I think if you look at both the Ukrainian situation and the Middle East, it is obvious that in the coming weeks and months there are really important potential developments, whatever timetables are going on in other countries.
“And that’s why I wanted to have this opportunity to talk directly to the President … about those decisions in the next few months, but to make sure that those decisions were, as it were, pitched in the wider strategic thinking that we share in relation to Ukraine, the Middle East and the Indo-Pacific.”
Sir Keir said the quickest way to resolve the conflict in Ukraine “lies through what Putin actually does”.
He said: “There’s only one reason we’re having these discussions, and that is Putin has illegally invaded Ukraine, and the quickest way to resolve this obviously lies through what Putin actually does, because it’s for him to end this.”
Mr Lammy and Mr Blinken were pressed on the use of Western weaponry during their visit to Ukraine earlier this week, but said they had to report back to their bosses, the Prime Minister and US President.
Mr Putin said allowing long-range strikes “would mean that Nato countries, the United States, and European countries are at war with Russia … if this is so, then, bearing in mind the change in the very essence of this conflict, we will make appropriate decisions based on the threats that will be created for us”.
Asked what he thought of Mr Putin’s threat of war, Mr Biden said: “I don’t think much about Vladimir Putin.”
Mr Biden thanked Sir Keir for his “leadership” during the Ukraine conflict, adding: “Putin will not prevail in this war”.
He said: “The United States is committed to standing with you to help Ukraine as it defends against Russia’s onslaught of aggression.
“It’s clear that Putin will not prevail in this war. The people of Ukraine will prevail.”
The US President said the two leaders would talk about Ukraine, the need for a hostage and ceasefire deal in the Middle East, and about the Indo-Pacific region.
He told the PM: “I’ve often said there’s no issue of global consequence where the United States and UK can’t work together and haven’t worked yet.”
Before the meeting began, a British reporter was told to “be quiet while I speak” by the US President as Mr Biden was asked about Mr Putin’s threat of war.
Concern about escalation has been one of the reasons why permission has not yet been given to Kyiv for the unrestricted use of Western weapons.
Iran has been hit with sanctions by the UK and US after the two countries formally accused Tehran of supplying ballistic missiles to Russia.
Mr Lammy and Mr Blinken announced further financial support for Ukraine, including a £600 million package from the UK and 717 million dollars (£550 million) from the US to meet immediate humanitarian, energy and stabilisation needs.
The UK package includes a reaffirmation of Rishi Sunak’s pledge of £242 million, as well as 484 million dollars (£371 million) worth of loan guarantees for World Bank lending before the end of the year, while the US package includes 325 million dollars (£250 million) to support Ukraine’s energy needs.
The PM and Mr Biden’s first White House bilateral took place as the Sir Keir attended the Nato summit just days after Labour won the election.
