Sen. John McCain (File)

Sources close to likely Republican presidential nominee John McCain have told U.S. news agencies the Arizona senator has settled on a vice presidential running mate.

McCain is expected to formally introduce his pick during a Friday morning rally in Ohio, the same day he celebrates his 72nd birthday.

The expected announcement would come a day after Democratic rival Barack Obama formally accepts his party's presidential nomination.  The Republican hopeful aired a television advertisement Thursday congratulating Obama on a "job well done" for his historic nomination.  But in a separate statement, McCain's campaign Thursday mocked the classic Greek-style columns on the stage for Obama's speech

One of those thought to be a top contender for McCain's running mate, Minnesota Governor Tim Pawlenty, canceled several public appearances in Denver on Thursday.  But it was unclear if there was any connection to the vice presidential pick.

Another possible choice, Senator Joe Lieberman of Connecticut, is drawing considerable fire from hardline conservatives over his support for abortion rights.  

Lieberman was Democrat Al Gore's vice presidential running mate in 2000, but has since become an independent due to his support for the U.S.-led war in Iraq.

Others believed to be under consideration by McCain include former Massachusetts Governor Mitt Romney and former Pennsylvania Governor Tom Ridge. 

Meanwhile, the Republican Party has adopted its campaign agenda ahead of next week's national convention in Minneapolis-St. Paul, Minnesota, where McCain will formally become the party's presidential nominee. 

Some information for this report was provided by AFP and AP.