WASHINGTON, July 26 (UPI) -- Republican U.S. presidential candidate John McCain's refusal to set a time line a U.S. troop pullout from Iraq is isolating him politically, observers say.

The Arizona senator had always had U.S. President George Bush in his corner in saying no timetables for troop withdrawals should be set, giving him a major ally in opposing the phased withdrawal advocated by likely Democratic opponent Sen. Barack Obama of Illinois. But now that Bush has agreed to consider a "time horizon" for troop drawdowns, McCain finds himself alone, The New York Times (NYSE:NYT) reported Saturday.

Responding to the situation, McCain said Friday that Obama's 16-month withdrawal proposal was "a pretty good timetable," although he was careful to add it must be based on battleground conditions, the newspaper said.

Bush's move toward pragmatism on Iraq and in dealing with North Korea has undercut McCain's policies, leaving him to the right of the administration, some Republicans say.

"Bush and Obama seem to be setting the foreign policy agenda, and McCain seems to be reacting," Kenneth Duberstein, a former chief of staff to the late President Ronald Reagan, told the Times.