No longer foes but not yet allies, President-elect Barack Obama and John McCain buried their bitter campaign in public smiles and searched for common ground in private on Monday, discussing possible collaboration on climate change, immigration, Guantanamo Bay and more.The 40-minute session at Obama's transition headquarters, their first meeting since Nov. 4 when Obama handily defeated McCain, was just the latest effort by the president-elect to heal wounds from the long and bitter campaign and seek help from his former rivals. On Thursday, he quietly met here with Sen. Hillary Rodham Clinton, his toughest rival for the Democratic nomination and now a possible choice for secretary of state.McCain's meeting with Obama was less furtive, and aides to both men said no Cabinet post is envisioned for the Arizona senator. Obama has said he plans to invite at least one Republican to join his Cabinet.Like Clinton, McCain knows that returning to the 100-member Senate will impose limits and frustrations after the heady two years of the presidential campaign. For both, a friendly relationship with the new president might open new opportunities in Congress or elsewhere, though they exchanged harsh words with him not long ago.For Obama, cordial ties to two of the nation's most famous and successful politicians might smooth the launch of an administration confronting an economic crisis and two wars.Before Monday's meeting, Obama said he and McCain would talk about "how we can do some work together to fix up the country." He thanked McCain "for the outstanding service he's already rendered."In a joint statement after the meeting, they vowed to work together to reform government and promote bipartisanship in Washington.Meanwhile, Clinton, who returns to Congress as a fairly junior senator with no immediate prospects for a leadership post, appeared very much in the running for secretary of state. Transition officials said she and her husband, former President Bill Clinton, were cooperating with a vetting process, although there were other contenders for the job.Bill Clinton's finances and business relationships could pose a conflict of interest for his wife if she became the nation's top diplomat. Since leaving the White House in 2001, he has amassed a multimillion-dollar fortune and built a large international foundation through his ties to corporations and foreign governments.As for Obama and McCain, they expressed similar views on a number of issues during the campaign, such as the dangers of climate change and a need to ease U.S. dependence on fossil fuels.Aides familiar with Monday's meeting said the two men spoke of working together on that broad issue, as well as on comprehensive immigration revisions, an effort McCain helped to spearhead in the Senate in 2006. The measure collapsed, and Obama will face difficult decisions in how far to push changes in immigration laws in a Congress dominated by Democrats.They also discussed the Guantanamo Bay detention camp, which both men have criticized and Obama has vowed to close.Obama also praised a proposal McCain has championed to establish a commission to reform "corporate welfare," aides said.They did not discuss specific legislation, the aides said. But Obama's incoming chief of staff, Rahm Emanuel, and South Carolina Republican Sen. Lindsey Graham, a close McCain friend and adviser, were expected to discuss a joint legislative effort. Emanuel and Graham participated in the meeting.Obama and McCain sat for a brief picture-taking session with reporters. They were heard briefly discussing football, and Obama cracked that "the national press is tame compared to the Chicago press."When asked if he planned to help the Obama administration, McCain replied, "Obviously."After the meeting, the two issued a joint statement saying: "At this defining moment in history, we believe that Americans of all parties want and need their leaders to come together and change the bad habits of Washington so that we can solve the common and urgent challenges of our time.""It is in this spirit that 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," they said. "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."Obama and McCain clashed bitterly during the fall campaign over taxes, the Iraq War, and ways to fix the ailing economy. Things got ugly at times, with McCain running ads comparing Obama to celebrities Britney Spears and Paris Hilton and raising questions about his relationship with a 1960s-era radical, William Ayers.Obama's campaign, meanwhile, labeled the 72-year-old McCain "erratic" and ran campaign ads deriding his economic views.The last time Obama and McCain issued a joint statement was Sept. 24, when they called for a bipartisan approach to the economic crisis. McCain quickly went his own way, however, announcing he was temporarily suspending his campaign and calling for a White House meeting that ended in chaos and hurt him in the polls.On Election Night, McCain paid tribute to Obama's historic ascendancy as the nation's first black president. The two agreed that night to meet after the election when McCain called Obama to concede defeat.