U.S. President Barack Obama phoned prime minister-designate Justin Trudeau Tuesday afternoon, congratulated him on leading his party to an election victory and teased him about his hair — or its colour, to be exact, predicting he could soon expect it to turn grey.

According to a readout of the call from the White House, the two leaders agreed on the importance of deepening the "already strong" bilateral relationship between Canada and the U.S. and committed to strengthen joint efforts to promote trade and to combat terrorism and climate change.

They talked about the recently concluded Trans-Pacific Partnership trade deal and committed to working together to "achieve an ambitious and durable" global climate change agreement at the upcoming United Nations conference in Paris in December.

At a news conference in Ottawa, Trudeau described the phone conversation as "warm" in tone and said that Obama advised him to cherish the time with his young children, because they grow up fast. Obama's two daughters are in high school and have grown up at the White House. Trudeau said the U.S. president also teased him about not having any grey hair.

"He said that I will probably get some quite soon, just like him," Trudeau said. The Liberal leader's hair was a theme before and during the campaign because of a Conservative attack ad that suggested Trudeau had a thin resumé and wasn't ready to lead Canada. "Nice hair, though," the ad said.

Relationship about more than Keystone

The Canadian election results were the first topic of conversation at the daily White House briefing earlier in the day. Press Secretary Josh Earnest was asked whether he expects the Canada-U.S. relationship to get easier under Trudeau because outgoing prime minister Stephen Harper seemed "annoyed" over the long delay on a Keystone XL pipeline decision.

"Well, I think it would be short-sighted to reduce the relationship between our two countries to just one issue," Earnest responded. The proposed cross-border pipeline recommendation is still pending at the State Department and has yet to get a final decision from Obama. 

Earnest said there are a number of issues that Canada and the U.S. work effectively on, including Canada's participation in the international coalition to fight ISIS in Iraq and Syria and the TPP trade deal.

Trudeau, who favours the construction of the Keystone XL pipeline, also said at the news conference that the Canada-U.S. relationship is about much more than a proposed pipeline and that he made that point when he spoke to Obama. In terms of the timing of a decision, Trudeau said he respects the president's role and responsibility in making it.

When pressed at the White House briefing about a decision, Earnest said Secretary of State John Kerry spoke about it earlier Tuesday and indicated the Canadian election result would have no bearing on the timing of a decision or on whether the answer will be yes or no.

Earnest said the White House does not have an expectation on when the State Department will complete its review and send its recommendation to Obama. The president does expect to make a decision, however, before he leaves office after the 2016 election, he said.

US Trudeau

Liberal Leader Justin Trudeau visited Washington, D.C., in the fall of 2013. He's pledged to make the U.S.-Canada relationship a more constructive one and blames outgoing Prime Minister Stephen Harper for weakened ties between the two countries. (Susan Walsh/Associated Press)

"Hopefully we'll get it done well before then, if for no other reason than we can stop talking about it," Earnest said.

Obama is under pressure from environmentalists to reject the TransCanada Corp.'s pipeline project that would connect Alberta's oil patch with refineries in the Gulf Coast.

Harper's government has lobbied for years in Washington for approval of Keystone. The outgoing prime minister has called the approval a "no-brainer," and Harper once said he wouldn't take no for an answer.

Obama understands ISIS position

Earnest noted on Tuesday that Canada has made some "important commitments" in advance of the Paris climate change conference but added: "We believe it's possible that there's more that Canada could do in this regard."

It's too early to judge whether Trudeau will follow through on environment policy promises made during the campaign, said Earnest, while also admitting he did not follow the campaign closely.

Obama has been pressing world leaders to make serious commitments to reduce greenhouse gas emissions in Paris, and that will be no different with Trudeau, he said.

Trudeau said he told the president during their call that it's important to him that Canada engages in a positive way on the environment file on an international stage. He also told Obama that he looks forward to demonstrating that "we have a Canadian government now that understands that the way to build a strong economy is to protect and defend our environment at the same time."

Trudeau has pledged to repair what he described as a frayed Canada-U.S. relationship under Harper but that could get off to a rocky start if he follows through on a promise to withdraw Canada's fighter jets from the U.S.-led fight against ISIS. The Liberals want to provide more humanitarian aid in Iraq and Syria and have Canada's military involved in training missions, not bombing missions.

The White House said it appreciates Canada lending its skill and expertise to the mission so far and hopes it can continue to count on its northern neighbour to participate in the coalition.

Trudeau said he and Obama spoke about Canada's role in the mission and that the president "understands the commitments I have made around ending the combat mission."

Harper can also expect a phone call from Obama in the near future, according to the White House spokesman.

"Our bilateral relationship has enhanced the security and prosperity of the American people and we certainly are appreciative of Prime Minister Harper's efforts to strengthen that relationship, and we look forward to building on that kind of progress when Mr. Trudeau takes over the Prime Minister's Office."