WASHINGTON- U.S. Sen. Tom Carper, D-Del., on Monday announced he is endorsing Hillary Clinton for president.

Delaware's senior senator issued the following statement on his endorsement of the Democratic candidate:

“Nearly 15 years ago, Hillary and I were elected to the United States Senate together, and since then I’ve had the joy and privilege of wishing my friend a happy birthday each year on Oct. 26. When I called her today, I had the opportunity to deliver a unique birthday message – that I am proud to endorse her as the next Democratic nominee for president.

“Out of deference and respect for another dear friend, Joe Biden, I withheld endorsing Hillary until today. Now that Joe has decided not to run, I am prepared to give Hillary my full and enthusiastic support.

“I’ve known Hillary for more than 20 years. My wife, Martha, and I think the world of her. She was a terrific First Lady, an exceptional senator and colleague, and a tireless secretary of state. She is the best candidate for the job as president, and I fully expect she will be elected next November.”

Other Democratic candidates for president include Vermont Sen. Bernie Sanders and former Maryland Gov. Martin O'Malley.