Biden levels with King Charles, PM Sunak before heading to Nato moot

US President Joe Biden Monday called on Britain's King Charles to deliberate on how to deal with the menace of climate change after visiting Prime Minister Rishi Sunak at 10 Downing Street in London.

After arriving at Stansted Airport on Sunday evening, he was transported to the US ambassador's residence in central London via helicopter. 

This stopover in Britain precedes a crucial two-day Nato summit in Vilnius, Lithuania, where leaders will deliberate on the situation in Ukraine and the future of the military alliance, with several nations expressing interest in joining.

Both sides played down the president's meeting with Sunak, their fifth in as many months, describing it as a continuation of long-running discussions, though it was Biden's first visit to the prime minister's Downing Street office as president.

"Great for us to carry on our conversations," Sunak told Biden as they sat in the Downing Street garden.

"We’ve got a lot to talk about," Biden replied. "Our relationship is rock-solid. Couldn’t be meeting with a closer friend and a greater ally. We've got a lot to talk about."

After spending less than an hour at Sunak's office, Biden headed to Windsor Castle to meet the king, the higher-profile part of his short British trip.

Biden, who skipped the king's coronation in May in line with the longstanding practice of US presidents, was expected to discuss climate change in Windsor, a cause on which Charles has campaigned for more than five decades.

The 74-year-old king greeted the 80-year-old president in the quadrangle of the castle, where he was given a guard of honour.

The men were due to have tea before discussing how to help boost private investment to combat climate change, a threat both leaders say is existential.

"The president has huge respect for the king's commitment on the climate issue in particular. He has been a clarion voice on this issue," White House national security adviser Jake Sullivan told reporters aboard Air Force One Sunday.

Their meeting comes at a moment when Sunak has faced criticism over his commitment to environmental issues.

Biden and Charles — who do not know each other well - had a phone conversation earlier this year that Sullivan described as "incredibly warm". Biden attended the funeral of Queen Elizabeth last year, and first lady Jill Biden attended the new king's coronation.

Ukraine Crisis

Sunak and Biden were due to share notes before the Nato summit in Lithuania, which kicks off on Tuesday and will be dominated by the Ukraine crisis.

Ahead of the trip, Biden urged caution for now on Ukraine's campaign to join Nato, whose mutual defence pact obliges all members to come to the aid of any member that is attacked.

"I don't think there is unanimity in Nato about whether or not to bring Ukraine into the Nato family now, at this moment, in the middle of a war," Biden said in a CNN interview that aired Sunday.

His trip comes a few days after he agreed to send US cluster munitions to Ukraine.

Such munitions are banned by more than 100 countries, including Britain, and are widely viewed as a threat to civilian populations because they typically release large numbers of smaller bomblets that can kill indiscriminately over a broad area.

Russia, Ukraine, and the US have not signed the Convention on Cluster Munitions, which bans their production, stockpiling, use, and transfer.

A spokesperson for Sunak said the US decision had been a difficult one, forced on Washington by Russia.