Sterling heads for biggest gain vs dollar since 1998

LONDON (Reuters) - Sterling was on course for its biggest one-day gain since 1998 on Tuesday, after Prime Minister Theresa May promised a parliamentary vote on Britain's deal to leave the EU and said the government wanted to remain a key European partner.

Sterling had stretched its rise to 2.9 percent on the day against the dollar to put it at an 11-day high of $1.2390.

Against the euro, the pound soared 1.8 percent - its biggest daily climb since before June's Brexit vote - to 86.38 pence.

(Reporting by Jemima Kelly; editing by Marc Jonese)