US PRESIDENT Joe Biden has announced that “the United States is back” as he began an eight-day European tour with a pre-G7 summit with British PM Boris Johnson today.

His first overseas trip as president is aimed at shoring up the Nato military alliance and ensuring the US’s allies stay in step with Washington’s increasingly confrontational approach to Russia and China. Mr Biden will attend the G7 meeting of leading Western economies in Cornwall on Friday before the Nato summit in Brussels kicks off on Monday.

“We’re going to make it clear that … democracies are standing together to tackle the toughest challenges and issues that matter the most to our future,” he said.

As he set out, the EU signalled its support for Mr Biden’s revival of the “lab leak” conspiracy theory over Covid-19’s origins, which was rejected by a team of international scientists sent to Wuhan, China — the first city struck by the virus — following an investigation earlier this year.

European Commission president Ursula von der Leyen said: “We have to know where it did come from in order to draw the right lessons and to develop the right tools to make sure that this will never happen again,” repeating US accusations that China did not fully co-operate with the initial investigation, though scientists from the mission itself have repeatedly dismissed this.

Also on Mr Biden’s schedule are a bilateral meeting with the European Union, a one-on-one with Turkish President Recep Tayyip Erdogan — whom France has accused of undermining Nato unity through its military activities in Syria, Libya and the Mediterranean — and talks with Russian President Vladimir Putin in Geneva.

Tensions with Moscow are high as US troops continue to lead Defender Europe 2021, a huge military exercise involving 28,000 troops from 16 countries conducting war games along Russia’s borders from the Baltic to the Black Sea.

The tour began with the eye-catching announcement that the US would donate 500 million Covid-19 vaccine doses to poorer countries, a move compared by his team to the US supplying Britain and the Soviet Union with materiel during the second world war.

“We were the ‘arsenal of democracy’ in World War II,” national security adviser Jake Sullivan told reporters. “We’re going to be the ‘arsenal of vaccines’ over this next period.”