Alarmed by the prospect of a Ronald Reagan presidency, the ALF-CIO is ready to swallow its deep reservations over President Carter's economics and mount an all-out drive to prevent a mass defection of blue collar workers to the former California governor.

"Reagan is just anathema to us," Alexander E. Barkan, the AFL-CIO's national political director said in an interview with the Associated Press yesterday. "I don't know of a single labor leader supporting him."

Without waiting for the political parties to choose nominees or for its leaders to make a formal endorsement, the labor federation is wasting no time trying to convince its 13.6 million members and their families that Reagan is no friend of workers.

To keep Reagan out of the White House, the AFL-CIO is prepared to campaign for Carter's reelection despite its unhappiness with him, assuming -- as it now appears -- he is the Democratic nominee.

Barkan, who heads the AFL-CIO's Committee on Political Education (COPE), said the federation will not formally endorse a candidate until September, but that the selection will certainly be a Democrat.

"The nominee appears to be Carter," Barkan said. "If he's the nominee, the general board will endorse him and we'll work like hell for him."

Barkan acknowledged that Reagan now appears to enjoy substantial blue collar support at the rank-and-file level. "But it's just temporary," he predicted. "When word on the Reagan program gets out," blue collar workers will abandon the GOP candidate, Barkan predicted.

Barkan also said independent presidential candidate John B. Anderson has a dismal labor record, a point that COPE hopes to impress upon liberal Democrats attracted by The Illinois Republican's positions on social issues, such as his support for the Equal Rights Amendment, gun control and federal funding for abortion for the poor.