Maybe it wanted to seal a deal with the mayor.

A young harbor seal (left) hauled itself up on a rock behind Gracie Mansion yesterday and stayed there to soak up the rays and snooze for about two hours.

Then it slipped back into the East River and swam off.

“I saw him and for the first 30 seconds, I was just kind of frozen, thinking how cute he is,’’ said Carina Berlin, 26, who was walking her dog before 9 a.m. when she spotted the creature.

“It’s very common to see harbor seals around Manhattan at this time of year,’’ said Julika Wocial, a marine biologist at the Riverhead Foundation for Marine Research and Preservation on Long Island.