Sterling struggled to bounce back from losses owing to renewed Brexit uncertainty after Boris Johnson proposed a general election to resolve the long-running saga, while Asian markets were mostly down after a broadly positive week.

File photo: VCG

With the prime minister giving up on a pledge to leave the EU by his Halloween deadline, he called for a December 12 national vote that would likely give his Conservative party enough MPs to eventually pass the agreement.

However, opposition lawmakers have said they will only vote for a snap poll if they are guaranteed Britain will not leave the EU without a deal, meaning there is a good chance his election bid will fail.

MPs will decide Monday on whether to agree to the election, just as the European Union is due to announce a three-month extension to the deadline.

The pound, which this week broke $1.30 for the first time in five months on optimism a no-deal Brexit will be avoided, went into retreat Thursday and held around the $1.2840 mark in Asia. The euro also extended gains against the British unit.

"A sense of rational optimism around Brexit has given way to more uncertainty as to the pound, and UK risk markets were roiled" by the prospect of an election, said AxiTrader analyst Stephen Innes.

He added that a national vote would amount to a referendum on Johnson's Brexit strategy.