WASHINGTON (CNN) -- Florida GOP Sen. Mel Martinez, whom President Bush endorsed to head the Republican National Committee, said Tuesday he will work hard to "strike a hopeful message" on behalf of his party.

"I'm going to be looking toward the future, and I'm going to try very hard to strike a hopeful message about what our party stands for," Martinez told reporters gathered outside the White House.

The senator made his comments after meeting with Bush, outgoing RNC chief Ken Mehlman, and other senior RNC officials. The president formally expressed his support for Martinez's bid following the meeting.

"He's going to be an excellent spokesman for the Republican Party," Bush said. "He'll be a person who'll be able to carry our message as we go into an important year in 2008."

Bush also praised Mehlman's efforts to expand the GOP base.

"It's been a joy working with you," Bush told Mehlman. "I appreciate the fact that you went to neighborhoods where Republicans have never been to talk to people about our message of ownership and hope."