"Quite frankly, I'm going to have to make a judgment in the next little while as to whether or not this Parliament can function productively," Harper told reporters while touring the Atlantic province of Newfoundland.
Harper heads a minority Conservative government that must rely on the support of at least one of the three opposition parties to get bills passed.
He complained about legislation being stalled in the Liberal-dominated Senate and obstructed in the House of Commons, principally by Liberal leader Stephane Dion.
"Two of the three opposition parties don't support the government and say we should be defeated. Mr. Dion says he doesn't support the government but won't say, you know, whether he will defeat us or not," Harper said.
"I don't think that's a tenable situation."
Harper, whose Conservatives defeated the governing Liberals in the January 2006 election, dared Dion last month to bring down the government or else let bills pass.
Polls point to another minority government if an election were held today. Support for the two main parties is roughly equal, with some polls showing the Conservatives in the lead while others have the Liberals ahead.
Harper had sought to take the ability to call elections at whim out of the hands of prime ministers, when early in his term he pushed a bill through Parliament that provides for a fixed election date of October 2009.
However, he retains the power to make any legislation a matter of confidence that would trigger an election if defeated, and he can also choose to put forward a direct confidence motion to test the opposition parties.