Canada's Governor General, Michaelle Jean, has cut short a trip to Europe to deal with a growing political crisis.
Opposition parties have united in a bid to topple the minority conservative government of Stephen Harper. It is less than two months since a general election.
Mr Harper has indicated he will ask for a temporary suspension of parliament to stop the opposition voting him out.
But if the vote happens and he loses, Ms Jean would ask the opposition to form a government or call a snap poll.
Ms Jean told the Canadian Broadcasting Corporation from the Czech Republic that her presence was required in Canada.
She was appointed in September 2005.
The BBC reports the opposition Liberals and New Democrats on Monday agreed to form an alliance, backed by the Bloc Quebecois, saying the government was failing to tackle Canada's economic problems.
They were also angered by proposals by Mr Harper, which have since been rescinded, to eliminate public financing of political parties - a move that would have hit them hard.
Mr Harper's Conservatives were re-elected with a stronger mandate in October, but failed to secure a majority and must rely on the support of the opposition to pass budgets and laws.
The confidence motion is scheduled for 8 December but Mr Harper has indicated he may seek the suspension of parliament until 27 January when the government is set to table its budget.