NDP Leader Jack Layton will meet with Stephen Harper on Saturday amid rampant speculation the prime minister is about to call an election.

Harper has sought meetings with all three opposition leaders to see if they can agree on an agenda for the fall session of Parliament, scheduled to begin Sept. 15.

Bloc Québécois Leader Gilles Duceppe has indicated he won't be available until Sept. 5 and Liberal Leader Stéphane Dion has indicated he'll be too busy to meet until Sept. 9.

"I gave [him] three dates: Sept. 5, 6 and 7," Duceppe told CBC News, adding he's still waiting to hear back from the Prime Minister's Office.

Speculation is rife that Harper will call a mid-October federal election before byelections are held Sept. 8 and 22 in four federal ridings.

Harper has argued that all three opposition parties are poised to topple the government shortly after Parliament returns, and he says he has a duty to jump before he's pushed.

Elections Canada announced Tuesday that advance voting for the byelections in Guelph, Ont., and the Quebec ridings of Saint-Lambert and Westmount-Ville-Marie begins Friday.

An Elections Canada official says there is nothing to prevent a general election call once advance polling begins.