John Kerry (search) put in a surprise appearance at the Yankees-Red Sox (search) baseball game Sunday night to throw out the opening pitch, making an early arrival in the city where Democratic delegates were gathering to nominate him for president.

Boston baseball fans followed their usual pattern of booing and cheering the person who throws out the pitch. Kerry, the crowd's hometown senator, kept smiling as he threw a ball that sank and hit the dirt before the catcher -- a soldier home from Iraq -- could catch it.

"It's great to be back in Boston for a game like this," Kerry said afterward. "Couldn't miss it."

Kerry arranged for his flight between the battleground states of Ohio and Florida to be diverted to Boston, where he had not been scheduled to make his grand entrance to the convention city until Wednesday evening. He said he had planned the trip in secret about a week ago.

"The idea of missing a Yankees-Red Sox series right before a convention week was not acceptable, so we changed the policy," Kerry told reporters on the plane.

Kerry threw out the first pitch to Spec. Will Pumyea, 23, a military police officer in the Massachusetts National Guard from Woburn, Mass., who had just returned from Iraq and who also had previously served in Afghanistan (search).

Kerry then watched the game from the owners' box with his wife, his two daughters, Pumyea, former Sen. John Glenn of Ohio, Red Sox owners John Henry and Tom Werner, and Katie Couric, the co-anchor of NBC's "Today" show who is dating Werner. Glenn fought in Korea with Ted Williams, the legendary Red Sox slugger.

Fans attending the game Sunday night did not have to go through metal detectors, which is the normal procedure for anyone attending an event with the Democratic presidential candidate. At Fenway Park, supporters distributed signs reading, "Sox Fans for Kerry."

The game was the third in the Boston homestand between the two fierce rivals -- who are also the teams representing the two convention cities. The Republicans gather in New York in late August. The Yankees won the first game Friday and the Red Sox came back with a dramatic two-run homer in the bottom of the ninth inning to win a fight-marred game Saturday.

In the clubhouse before the game, Kerry said: "I've got to win New York, but I do want the Red Sox to win."

Kerry planned to fly on to Florida on Sunday night after the game and resume his schedule.