Veteran U.S. Senator Bernie Sanders joined striking British workers at a trade union rally in London on Wednesday, saying workers need to stand together to fight back at what he called "corporate greed" and billionaires amassing more wealth.

The event was hosted by the RMT union, which has been at the heart of strikes that have crippled Britain's transport network in recent months as workers demand better pay and conditions to counter the impact of soaring energy price-driven inflation.

"People across the world need to stand together to tell the oligarchs they cannot have it all," Sanders told the gathering at the Trade Union Congress headquarters.