President Joe Biden brushed off a threat from Russian leader Vladimir Putin about war against the West if Ukraine's allies allow it to use weapons deeper inside Russia. It's a shift that Kyiv has pleaded for but does not appear likely to be announced following a meeting Friday between Biden and Britain's prime minister.

Ukraine and many of its supporters in the US and Europe want Biden to lift restrictions on Western-provided long-range weapons, and there are signs Biden might shift the administration's policy.

But the US, concerned about any step that could lead Russia to escalate the conflict, has moved cautiously before granting a series of earlier requests from Ukraine for specific arms, including advanced tanks, missiles and rocket systems, and F-16 fighter jets. Russian officials have issued similar threats before many of those past decisions.

Ukraine was a key topic for Biden and British Prime Minister Keir Starmer following this week's visit to Kyiv by their top diplomats, who came under fresh pressure to loosen weapons restrictions. So far, the US has allowed Ukraine to use American-provided weapons only in a limited area inside Russia's border with Ukraine.

Two US officials familiar with discussions said they believe Starmer will seek Biden's approval to allow Ukraine to use British Storm Shadow missiles for expanded strikes in Russia. Biden's approval may be needed because Storm Shadow components are made in the US. The officials, who spoke on condition of anonymity to share the status of private conversations, said they believed Biden would be amenable.

No announcement was expected Friday, several US officials said.

Putin said a day earlier that allowing long-range strikes “would mean that NATO countries, the United States and European countries, are at war with Russia.” His remarks were in line with the narrative the Kremlin has promoted since early in the war, accusing NATO countries of de-facto participation in the conflict and threatening a response.

Speaking to journalists shortly before the talks with Starmer, Biden said he wanted to make “clear that Putin will not prevail in this war.”

Asked what he thought about Putin's threat, Biden answered, “I don't think much about Vladimir Putin.”

Sitting at a table across from Biden before their closed-door meeting, Starmer said, “I think the next few weeks and months could be crucial” for the war.

Ukrainian President Volodymyr Zelenskyy has been pressing the US and other allies to allow his forces to use Western weapons to target Russian air bases and launch sites far from the border as Russia has stepped up assaults on Ukraine's electricity grid and utilities before winter.

“The war must become more difficult for Russia — that is the only way to make them realize it must end," he posted Friday on social media.

Zelenskyy's appeal has garnered support in US and European security and diplomatic circles, including from some former U.S. generals and diplomats, lawmakers and security analysts. They argue that Russia's previous threats of escalation against the West have proven hollow and that the U.S. restrictions on weapons are making it impossible for Ukraine to gain the battlefield momentum it needs.

Even a few Ukrainian strikes with heavier weapons on military targets deeper into Russia would put more strain on Russian logistics, troops and other resources, said George Barros, a security analyst for the Institute for the Study of War.

Defense Secretary Lloyd Austin stressed Friday that decisions on what military support to provide Ukraine were complex, saying, “There is no silver bullet when it comes to things like this.” He noted last week that Ukraine has already been able to strike inside Russia with its own internally produced systems, including drones.

Zelenskyy wants more long-range weaponry from Washington, including the Army Tactical Missile System, known as ATACMS, for strikes in Russia.

Lt. Col. Charlie Dietz, a Pentagon spokesperson, said ATACMS would not be the answer to the main threat Ukraine faces from long-range Russian glide bombs, which are being fired from more than 300 kilometers (185 miles) away, beyond the reach of ATACMS.

American officials also do not believe they have enough of the weapon systems available to provide Ukraine with the number to make a substantive difference on the ground, one of the US officials said.

Biden, however, has hinted that a change could be afoot. In an exchange with reporters this week about whether he was ready to ease weapons restrictions on Ukraine, he responded, “We're working that out now.”

Some American supporters of Ukraine have criticised the Biden administration for telegraphing earlier decisions on beefing up weapons to Kyiv well in advance, saying the US was giving Russia ample time to update its tactics accordingly.

Biden and Starmer, meeting for the second time since his centre-left government was elected in July, were expected to compare notes on the war in Ukraine, the languishing efforts to get a cease-fire deal in Gaza, mutual concerns in the Indo-Pacific and other issues before this month's annual meeting of global leaders at the UN General Assembly.

Russia accused six British diplomats of spying Friday and said it would expel them. Starmer's government called the accusation baseless and linked it to Britain's expulsion of Moscow's defense attache in London over spying allegations in May.

The White House also has tried in recent days to put a greater emphasis on the nexus between the war in Ukraine and the conflict in the Middle East that was sparked after Iranian-backed Hamas militants in Gaza attacked Israel on October 7.

The Biden administration said this week that Iran recently delivered short-range ballistic weapons to Russia to use against Ukraine, a transfer that White House officials worry will allow Russia to use more of its arsenal for targets far beyond the Ukrainian front line while employing Iranian warheads for closer-range targets.

“It certainly speaks to the manner in which this partnership threatens European security and how it illustrates Iran's destabilizing influence now reaches well beyond the Middle East,” White House national security spokesperson John Kirby said.