RPT-Euro, sterling rise to session highs versus US dollar

NEW YORK, May 21 (Reuters) - The euro and sterling extended gains against the U.S. dollar on Thursday to briefly touch session highs.

The euro rose to a session peak of $1.3901, according to electronic trading platform EBS, and was last up 0.8 percent on the day at $1.3880 EUR=.

The pound hit a session high at $1.5883 GBP=, up 0.8 percent, according to Reuters data. It had earlier tumbled as much on news that Standard & Poor's is considering a downgrade of the U.K.'s triple-A credit rating. (Reporting by Wanfeng Zhou, Editing by Chizu Nomiyama)