With the deadline looming for Canada to decide whether to extend its 30-day military advisory mission in Iraq, the opposition is accusing Prime Minister Stephen Harper of holding back key information on military talks with the United States.

A spokesperson for the U.S. Secretary of Defense said Thursday that Canada sent the U.S. a letter asking for more details on how it could contribute to coalition efforts in the fight against Islamic State militants in Iraq.

The U.S. then replied with a letter describing ways Canada could provide assistance, according to the DoD.

Prime Minister Stephen Harper told a business audience in New York City Wednesday that the U.S. had asked 鈥渇or some additional contribution鈥 and that his government is 鈥渨eighing our response.鈥

that Canada did receive an initial letter from the U.S., but it was a form letter sent to all allies in mid-September, not a special request to the Harper government.

In a statement issued late Thursday, Liberal Leader Justin Trudeau accused Harper of 鈥減laying coy political strategy games and fudging the truth.鈥

鈥淚t now appears as though the Prime Minister omitted a key detail about the American request for further Canadian participation in Iraq,鈥 Trudeau said. 鈥淚t was not the U.S. asking Canada for help. It was the other way around.鈥

But Harper鈥檚 director of communications, Jason MacDonald, told The Canadian Press that Canada has always said it would listen to requests for help in the fight against ISIS.

"It was in response to those conversations that we received a letter," MacDonald said.

In his statement Thursday, Trudeau also called on Harper to present his plan for Canada鈥檚 involvement in Iraq.

鈥淎ny change to Canada鈥檚 non-combat mission in Iraq must only be made with rigorous and effective Parliamentary oversight,鈥 Trudeau said. 鈥淲e expect the Prime Minister to answer all questions pertaining to this deployment fully and openly in the House of Commons in front of Canadians.鈥

Foreign Affairs Minister John Baird said Thursday that the issue would be put to a vote in the House of Commons.

"If there's a combat mission, I think the prime minister has always been very clear, that would go before Parliament for a vote, that has not changed," Baird told reporters at the United Nations.

MPs demand answers

Earlier Thursday, NDP Leader Thomas Mulcair and other opposition MPs demanded to be informed of the contents of the letter requesting Canada鈥檚 help in Iraq.

Mulcair also noted that Harper had previously said that Canadian military missions would require a vote in the House.

鈥淭here鈥檚 been no debate organized by them, no real information given to Canadians or to Parliamentarians, and there鈥檚 no vote,鈥 .

鈥淲e鈥檙e concerned about that.鈥

Mulcair added: 鈥淲hat鈥檚 more important that you can decide in the life of your Parliament or your country than whether or not you send women and men to fight in a war where they could die? So this is a very serious matter and it鈥檚 something that requires the proper attention based on full information.鈥

Earlier in question period, Mulcair had called on the federal government to go public with the letter that U.S. officials sent with the troop request, so Canadians and Parliamentarians can be clear of its nature and timing.

鈥淗ow many additional soldiers were requested by the United States and how many additional soldiers does the prime minister intend to send?鈥 Mulcair asked.

Defence Minister Rob Nicholson said the request for additional support 鈥渨ill be part of the review by the government at the end of the 30-day period, and we鈥檒l make a decision.鈥

Liberal MP Marc Garneau asked whether the government will consult Parliament if it considers expanding Canada鈥檚 role in Iraq. Nicholson did not respond to the request directly, saying only that the government has been forthcoming with mission details in both briefings to the opposition and in committee.

Nicholson responded to a similar question from MP Joyce Murray by adding that the NDP and the Liberals can use their opposition days in the House to launch a debate on the Iraq mission.

Mulcair took another turn and asked directly for a vote in the House, a request Nicholson did not directly address.

After several days of questions in the House about when Canada鈥檚 mission in Iraq officially began, Parliamentary Secretary to the Defence Minister, James Bezan, confirmed Wednesday that the 鈥渃lock started running鈥 on Sept. 5.

That leaves just over a week to go before the government must decide whether to extend the mission. Canada currently has 69 special ops soldiers in Iraq, training and advising Iraqi soldiers in their fight against Islamic State militants.

A senior government source told 麻豆影视 Wednesday that Canada is considering doing more to support the fight, but the source said Canada will not be committing troops to a combat role.

The prime minister avoided commenting on ISIS during a speech to the United Nations General Assembly on Thursday, instead opting to focus on child and maternal health.

With a report from CTV's Deputy Ottawa Bureau Chief Laurie Graham and files from The Canadian Press