Five-time champion Roger Federer needed five sets to overcome American teenager Frances Tiafoe in the first round of the US Open.

The 36-year-old Swiss won 4-6 6-2 6-1 1-6 6-4 in his first ever match under the Arthur Ashe Stadium roof.

Third seed Federer goes on to face Slovenia's Blaz Kavcic or Mikhail Youzhny of Russia on Thursday.

Only nine players completed their matches as rain wiped out much of Tuesday's schedule.

Top seed Rafael Nadal beat Serbia's Dusan Lajovic 7-6 (8-6) 6-2 6-2, before American 15th seed Madison Keys opened the night session with a 6-3 7-6 (8-6) victory over Belgian Elise Mertens.

They benefited from the stadium-court roof, which was not in place when Federer last played at Flushing Meadows two years ago, a knee injury forcing him out 12 months ago.

A crowd of almost 24,000 packed in to see his return to New York, but 19-year-old Tiafoe ensured they saw a far closer contest than expected.