The White House says Justin Trudeau's and Barack Obama's progressive values and shared commitment to tackling global warming ignited a "special relationship" that will result in signature announcements on climate change and cross-border trade.

In a briefing in advance of the Prime Minister's official visit to Washington, senior U.S. officials highlighted the similarities between Mr. Trudeau and President Obama and the promise of an "ambitious" bilateral partnership.

"There is developing a special relationship between this President and the Prime Minister," said Mark Feierstein, a high-ranking member of Mr. Obama's National Security Council. "Both are young leaders with similar visions. Both have a progressive vision of governance. Both are committed to appropriate use of multilateral tools. Both are committed to diversity."

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While reluctant to comment on strained relations with the former Conservative government over the environment and the Keystone pipeline, Mr. Obama's special envoy for climate change, Todd Stern, was effusive in describing Mr. Trudeau's approach.

"I will say the climate relationship with Canada really just ramped up dramatically and quickly," Mr. Stern said. "The commitment of both leaders to address this global challenge is real and I expect under their leadership North America will make significant progress this year."

Mr. Stern said the two leaders will unveil environmental initiatives to protect the Arctic, set fuel and emission standards for heavy vehicles and reduce methane gas and so-called black carbon from burning fossil fuels.

Conservative foreign-affairs critic Tony Clement said the measures on methane and black carbon were already "in the pipeline" when Mr. Trudeau assumed power. "I just would say to the Prime Minister, don't try to build this up to be something that it isn't because, ultimately, in terms of substance, this is going to be a relatively substance-free visit," he said.

U.S. officials were reluctant to offer concrete details of Thursday's expected announcements but said they would include border-security measures such as U.S. Customs preclearance for manufacturing plants in Canada.

"I don't want to get ahead of what the Prime Minister and the President may be announcing on Thursday but I would anticipate that would be a focal point of their discussions," Mr. Feierstein said.

However, White House officials identified one potential area of conflict, namely Mr. Trudeau's reluctance to publicly endorse the Trans-Pacific Partnership negotiated by the former Conservative government. The Prime Minister had said he wants to hold public consultations before pronouncing on the 12-nation trade pact.

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"It is obviously very, very high on the agenda. Among all the trade issues it is probably at the top. Obviously a very important issue for this administration, for President Obama," Mr. Feierstein said. "Obviously we defer to [Mr. Trudeau] and his team as to what he will anticipate saying or not saying during the visit."

The Americans were also tight-lipped about the chances of a concluding a new softwood lumber deal during the Oval Office talks. The 2006 softwood lumber deal expired last October and both countries have until this fall to reach a new agreement or face the possibility that the U.S. Congress and American lumber producers will seek punitive duties against Canadian exports.

Mr. Trudeau will arrive in Washington on Wednesday evening for three days of events including the first U.S. state dinner for a Canadian leader in 19 years. He will also speak to progressive think tanks, take questions from university students and lay a wreath at Arlington National Cemetery.