Britain sanctioned Abramovich in a crackdown on Russian oligarchs after Moscow's invasion of Ukraine in 2022, triggering a rushed sale of the Premier League club and freezing of the proceeds.

Britain wants the funds spent only in Ukraine in line with a wider European push for Moscow to foot the bill for the deaths and destruction triggered by its invasion. Abramovich is seeking more flexibility and wants the money to go to all victims.

In a rare joint statement, British finance minister Rachel Reeves and foreign minister David Lammy said on Tuesday the government was ready to step up efforts to secure the money.

"The government is determined to see the proceeds from the sale of Chelsea Football Club reach humanitarian causes in Ukraine, following Russia's illegal full-scale invasion. We are deeply frustrated that it has not been possible to reach agreement on this with Mr Abramovich so far," they said.

They said the door for negotiations would remain open but that they were "fully prepared to pursue this through the courts if required".

A lawyer for Abramovich in Britain did not immediately respond to a request for comment.

Reuters reported in March that Britain was considering legal action over the issue.

Under Abramovich, Chelsea enjoyed the most successful run in its history before the club was sold to a consortium led by US investor Todd Boehly and private equity firm Clearlake Capital in May 2022.

Proceeds from the sale are frozen in a British bank account. They cannot be moved or used without a license from the Office of Financial Sanctions Implementation, the agency in the finance ministry that enforces sanctions.