With star-spangled banners, cookies and 'Stop Trump' leaflets, US campaigners living in Britain took to the streets of London in a double-decker bus on Wednesday to persuade compatriots to vote.

Setting off from University College London, the red bus drove around the British capital, stopping in the City financial hub and at the Houses of Parliament in an attempt to find US expats to win over.

Around 20 campaigners chanted anti-Trump slogans and handed out leaflets telling US citizens to register to vote and to pick Democratic candidate Hillary Clinton over the Republican choice Trump.

US campaigners living in Britain took to the streets of London in a double-decker bus on Wednesday to persuade compatriots to vote

Activists ride on a 'Stop Trump' bus in London on Wednesday in a campaign to mobilise US expatriots to register to vote in the US presidential election

The event Wednesday was organised by the global online campaign movement Avaaz as the deadline to register to vote is approaching in some American states

The event was organised by the campaign group Avaaz.

'We know that Americans abroad don't generally vote but we know that they're incredibly progressive so this could be the game-changer for this year's election," Avaaz campaign director Meredith Alexander said.

The 'Stop Trump' bus went over Westminster Bridge on Wednesday

Signs on the bus read 'Americans Abroad: Vote to Stop Trump'

The red double-decker bus journeyed by the Houses of Parliament on Wednesday

Alexander said there were around eight million US citizens living outside the country, which altogether could constitute a 'swing state' in the November election.

'It's absolutely vital that we mobilise this secret swing state so that can defeat Trump,' she said.

Campaigners were pictured with their faces painted with both the Union Jack and the US flag

Republican presidential nominee Donald Trump delivers remarks as he rallies with supporters in Toledo, Ohio, on Wednesday

Avaaz said there were around 220,000 Americans living in Britain

Avaaz said there were around 220,000 Americans living in Britain.

One of them, Michael Dale, a 70-year-old law lecturer, was on board the anti-Trump bus.

'I am voting for Hillary Clinton. I think there's no choice,' he said, as the campaigners handed out cookies and Johnny Cash music played in the background.

Avaaz is planning similar campaign initiatives in Mexico and Berlin later this week.

Around 20 campaigners chanted anti-Trump slogans and handed out leaflets telling US citizens to register to vote and to pick Democratic candidate Hillary Clinton over the Republican choice Trump

One woman held a sign which read 'UK and US: United to Stop Trump'