President Obama paid tribute to America's men and women in uniform tonight as he kicked off the White House Fourth of July celebration, telling service members gathered on the South Lawn that they "represent what is best in America."

"You serve under our proud flag. You and your families sacrifice more than most of us can ever know - all in defense of those God-given rights that were first put to paper 236 years ago: life, liberty, and the pursuit of happiness," he said. "So as your commander-in-chief - but also as an American - I want to invite all of you over to say one thing: Thank you."

The president saluted this "generation of heroes" for its service and sacrifice.

"I want you all - our men and women in uniform, our veterans and their families -to know this: America will always remember. We will always be there for you, just as you've been there for us. That's my promise. That is America's promise. And that is one that we pledge to fulfill on this Independence Day," he said.

Get more pure politics at ABC News.com/Politics and a lighter take on the news at OTUSNews.com

The president and first lady welcomed service members and their families for a barbeque and concert at the White House and, of course, to see the fireworks. Families braved the sweltering heat to enjoy the celebration and meet the president.

"Are you hot? It's supposed to be hot. It's the Fourth of July," the president, dressed down in khakis and a polo shirt, said at the top of his brief remarks.

"Today, all across America, at schools and beaches, and in town squares, Americans are celebrating the freedoms that all of you and your families defend. Like many of them, we're grilling in the backyard," he joked.

Hot dog and hamburger stands were set up on the South Lawn. Cotton candy and popcorn were also on the menu. Children enjoyed face painting and balloon animals and, later tonight, guests will be treated to a concert by country crooner Brad Paisley.