Prime Minister Justin Trudeau is sticking to his promise of pulling Canada out of the bombing campaign against the Islamic State, despite a request for more military help from the US government.

Renee Filiatrault, spokesperson for Canadian Defense Minister Harjit Sajjan, confirmed to VICE News on Monday that he has received a letter from US Defense Secretary Ashton Carter, which asked for more contributions in the fight against IS militants.

Similar letters were reportedly received by other members of the US-led anti-IS coalition, including Germany and Australia.

"Canada has an important role to play on the world stage and we remain committed to working with our allies," said Sajjan in an email. "We are currently reviewing our military contribution to the multinational coalition against ISIS and discussions remain ongoing both within government and with our allies."

Filiatrault confirmed that Canada's plans to pull out of the bombing mission have not changed. She said details about how Canada will contribute to the mission are expected in the coming days.

During his campaign, newly-elected Prime Minister Trudeau promised to remove Canada's six CF-18s, which are participating in airstrikes against the militant group in Iraq and Syria, from the region.

However, a date for the withdrawal hasn't been set, and the most recent airstrikes happened as recently as Sunday, with two CF-18 Hornets successfully striking an IS fighting position northwest of Mosul, according to the Operation IMPACT website.

German Chancellor Angela Merkel publicly dismissed the American request on Sunday.

"I believe Germany is fulfilling its part and we don't need to talk about new issues related to this question at the moment," she told broadcaster ZDF. This comes after the German parliament voted in favor of joining the anti-IS military campaign in a non-combat role.

Australian minister Marise Payne told reporters on Saturday that the request was being considered, but that Australia "is already making a very significant commitment."

On Monday, President Barack Obama reiterated America's resolve in fighting the Islamic State.

"As we squeeze its heart, we'll make it harder for ISIL to pump its terror and propaganda to the rest of the world," he said at the Pentagon. "ISIL leaders cannot hide and our next message to them is simple: You are next."