Speaking in the Oval Office, Biden said he wanted to reiterate that he "fully, fully supports Sweden's membership in NATO."

Biden added he was "anxiously looking forward" to the bid being ratified.

Kristersson thanked the US president for his leadership in maintaining "transatlantic unity" during the upheaval sparked by Russia's invasion of Ukraine. He also praised Biden's "strong support" for Sweden's NATO bid, which is being held up by Turkey and Hungary.

The Oval Office meeting kicked off a string of diplomatic events for Biden centered on NATO.

He leaves Sunday for a one-day trip to close ally Britain, then attends the annual NATO summit in Vilnius and finishes up with a stop in the alliance's newest member Finland.

Both Finland and Sweden dropped their official neutrality to request NATO entry in response to Russia's 2022 invasion of neighboring Ukraine. Biden sees the bloc's expansion and its mammoth efforts to arm and support Ukraine's forces as a strategic defeat for Moscow -- and his own biggest diplomatic achievement.

But expansion of NATO requires unanimous ratification from the existing 31 members.

White House Press Secretary Karine Jean-Pierre would not say whether Biden planned to reach out directly to his counterparts in Turkey and Hungary before the summit.

"He's been pretty, pretty steadfast" on the need to approve the application, she said. "Sweden is a strong, capable defense partner that shares NATO's values."

In addition to discussing efforts to bolster Kyiv during its difficult counteroffensive to oust Russian troops occupying swaths of Ukraine's east and south, the two leaders also discussed transatlantic coordination on China, climate change and emerging technologies.

- Turkey refuses 'time pressure' -

Western officials had hoped to formally welcome Sweden into the bloc before next Tuesday's summit.

After his meeting with the US president, Kristersson said that he and Biden had agreed that the "Vilnius meeting in a week is certainly appropriate time for Sweden's entry, but only Turkey can take Turkey's decisions."

Turkish President Recep Tayyip Erdogan, however, has frustrated Western leaders by linking approval for Sweden to demands that Stockholm crack down on members of opposition Kurdish movements, such as the Kurdistan Workers' Party PKK, which Turkey says is a terrorist group.

Sweden says it met those demands, but another flashpoint has emerged over a protest outside a Stockholm mosque where an Iraqi man set fire to pages from the Koran.

On Tuesday, Turkish Foreign Minister Hakan Fidan rejected making the NATO summit a deadline, saying "we never approve of the use of time pressure as a method."

Hungary has indicated it will follow Turkey's lead in the dispute.

Hungarian Foreign Minister Peter Szijjarto said Tuesday he had been holding regular consultations with Fidan about Sweden.

Top diplomats from Turkey and Sweden will meet Thursday at NATO headquarters in Brussels.

The diplomatic activity comes as Ukraine is in the early phases of a long-promised push to try and liberate territories occupied by Russia.

The Biden administration is hoping success in that offensive will buoy public opinion ahead of the 2024 presidential election, where generous US aid to Ukraine may become a contentious issue.