AFSCME is the largest union for workers in the public service sector with 1.4 million members nationwide.
Obama reached out to union presidents and leaders Thursday in hopes of quickly unifying the nation's labor movement behind his candidacy after a grueling primary contest with Clinton. The New York senator and former first lady ceded the nomination to him earlier this month.
McEntee was one of Clinton's most outspoken supporters throughout the primary, and his union was one of the biggest to jump aboard her campaign early in the primary.
McEntee also is chair of the Political Education Committee for the AFL-CIO - the nation's largest labor organization - which did not endorse in the Democratic primary.
But McEntee on Wednesday praised Obama as a "sure-footed friend of labor" after he and other AFL-CIO leaders met with the Illinois senator at AFL-CIO headquarters, which is a block from the White House. Union leaders said after that meeting that an AFL-CIO endorsement could come within weeks once its international leadership has a chance for a formal vote.
McEntee praised Clinton, and said that he agreed with her statement that the best way to continue the fight was to "do all we can to help elect Barack Obama the next president of the United States."
AFSCME represents government and private workers including nurses, bus drivers, child care providers, custodians and librarians.
In his meeting, Obama told union leaders that he will pursue economic policies that benefits workers if elected president, but he also will seek input from corporate leaders.
"The economy is not working the way it should be, and that's going to be the goal of an Obama presidency - to make sure we've got bottom-up economic growth instead of the kind of tired, worn-out, trickle-down ideologies we've been seeing for so many years," Obama said as he gathered with about three dozen leaders in a Capitol Hill hotel.
Obama has been working to unite the labor movement behind his candidacy in a series of meetings during two days in Washington, including with some leaders who supported his primary rivals.
Obama said unions will be "a critical ingredient" in restoring fairness and prosperity to the economy, but he also made clear they wouldn't be the only ones with input.
"I'm going to meet with corporate CEOs sometime next week to hear from them about what they think we need to do to make the economy more competitive," he said. "But I want everybody here to understand the reason we wanted to organize this is that if our economy is not benefiting the average person ... then it's not doing its job.
"In fact, the economy, for big chucks of the last eight years, has actually grown," Obama said. "The problem is that all the benefits have gone to a handful of people and the vast majority has seen their actual income and wages go down effectively at the same time as the price of everything from gas to food has gone up."
