U.S. President-elect Barack Obama and Senator John McCain (R-AZ) during a meeting in Obama's transition office in Chicago, November 17, 2008.

(L-R) Senator Lindsey Graham (R-SC), Senator John McCain (R-AZ), President-elect Barack Obama and his chief-of-staff Rahm Emanuel during a meeting in Obama's transition office in Chicago, November 17, 2008.

U.S. President-elect Barack Obama smiles during a meeting in Obama's transition office in Chicago, November 17, 2008.

WASHINGTON, Nov. 17 (Xinhua) -- U.S. president-elect Barack Obama and his former Republican presidential rival, John McCain, vowed on Monday to "launch a new era of reform" and work together on "critical challenges."

"We had a productive conversation today about the need to launch a new era of reform where we take on government waste and bitter partisanship in Washington in order to restore trust in government, and bring back prosperity and opportunity for every hardworking American family," said a statement by Obama's transition office in Chicago, Illinois.

"We hope to work together in the days and months ahead on critical challenges like solving our financial crisis, creating a new energy economy, and protecting our nation's security," it said.

The two who have been competing for the White House for months met again in Obama's transition headquarters for the first time since the Nov. 4 presidential elections.

They sat together for a brief picture-taking session with reporters, with Rahm Emanuel, Obama's nominated White House chief of staff, and South Carolina Republican Sen. Lindsey Graham, McCain's close friend, at present.

Before the meeting, Obama said that he would talk about how they could continue to work together, and offer his gratitude to McCain for all his service so far.

Obama and McCain have co-worked in the Senate for three years before they started their presidential campaignseparately.

When asked if he would help the Obama administration before the meeting, McCain said "obviously."

Obama has repeatedly promised during his historical presidential campaign that he would reach out to Republicans to work in his government should he be elected.

However, aides to both men have said that it was unlikely McCain, who is still in his fourth term in the Senate, would serve in an Obama Cabinet.