SAN DIEGO (AP) -- Republican presidential candidate Mitt Romney is promising to maintain an American military "with no comparable power anywhere in the world."

The presumptive Republican presidential nominee faced a San Diego crowd estimated at 5,000 on Monday in what was billed as a Memorial Day service, not a campaign rally. But he drew clear contrasts with President Barack Obama.

Romney is warning against shrinking America's military in Europe's image.

He says America must have the world's strongest military to win wars and to prevent them.

Romney was joined by Arizona Sen. John McCain, a Vietnam veteran who says Romney is "fully qualified" to be the nation's commander in chief.

Obama paid tribute to veterans in the Washington area Monday.

A new Gallup poll shows veterans prefer Romney over the president.