NEW YORK, March 16 (Reuters) - The euro extended gains versus the dollar on Tuesday to hit a session high after Standard & Poor's affirmed its ratings on Greece.

S&P said the outlook on the rating is negative, however, indicating a downgrade is still likely over the long term. For details see [ID:nWNA6076].

The euro rose as high as $1.3771 EUR=, according to Reuters data, and was last at $1.3760, up 0.6 percent on the day. (Editing by James Dalgleish)