DENVER, Aug 28 (Reuters) - A top contender to be Republican John McCain's vice presidential running mate abruptly canceled appointments in Denver on Thursday but it was unclear whether he was McCain's choice.

Minnesota Gov. Tim Pawlenty, in Denver to help provide counterattacks against the Democratic Party convention, canceled participation in a news conference and other appearances, a Republican official said.

It was unclear whether the cancellation had any significance to McCain's vice presidential search.

Pawlenty, 47, was believed to have been on McCain's short list for vice presidential running mates, a list that also included former Massachusetts Gov. Mitt Romney, who lost to McCain in the primary battle, and independent Democratic Sen. Joe Lieberman of Connecticut.

A Republican official said McCain has made up his mind on his No. 2 and was expected to appear with his running mate at a rally on Friday in Dayton, Ohio.