Justin Trudeau, the prime minister of Canada, met with President Obama on Thursday for the first official visit by a Canadian leader in 19 years, a diplomatic honor made possible in part by new pledges of cooperation on combating climate change.

Mr. Obama and Mr. Trudeau announced Thursday morning new commitments to reduce planet-warming emissions of methane, a chemical contained in natural gas that is about 25 times as potent as carbon dioxide and that can leak from drilling wells and pipelines.

In a joint statement, the leaders promised that their two countries would ” play a leadership role internationally in the low carbon global economy over the coming decades.” As part of the announcement, United States officials said they would immediately begin a new push to regulate methane emissions from existing oil and gas facilities, though finishing that process before the end of Mr. Obama’s tenure is unlikely.

“Methane is upwards of 20 times more potent than carbon dioxide in warming the planet,” said Gina McCarthy, the administrator of the Environmental Protection Agency. “It has become clear that it is time for the E.P.A. to take additional action to regulate existing sources in the oil and gas sector.”

Mr. Obama and Mr. Trudeau also pledged new cooperation in preserving the Arctic and focusing on biodiversity, science-based decision-making, indigenous people and building a sustainable Arctic economy. The two nations also promised to accelerate the carrying out of agreements made in climate talks in Paris last year.

“Both nations know we must care for the one planet we share,” said Sally Jewell, the secretary of the interior in the United States. “I appreciate Canada’s strong leadership.”

The climate announcements came before a day of ceremony that will conclude with a state dinner in the East Room of the White House. On the menu is Alaskan halibut casseroles, roasted apricot galette, baby lamb chops with Yukon Gold potato dauphinoise and a maple pecan cake with cocoa nib wafer and butterscotch swirl ice cream.

The arrival of Mr. Trudeau and his wife, Sophie Grégoire-Trudeau, has prompted comparisons to a similar visit in 1977 by Pierre Trudeau, a former prime minister and the current leader’s father. That visit made headlines when Margaret Trudeau, the prime minister’s wife, wore an above-the-knee dress to the White House state dinner.

While Canada and the United States have long been close allies, Mr. Obama’s efforts to confront global warming had become a major point of contention with Mr. Trudeau’s predecessor, Stephen Harper, who sought to aggressively expand Canada’s oil industry.

As Mr. Obama became more determined to leave behind a lasting environmental legacy, he delayed and eventually rejected construction of the Keystone XL pipeline, which would have transported nearly a million barrels a day of heavily polluting oil from Alberta to refineries on the Gulf Coast.

Mr. Obama’s rejection of the pipeline severely strained relations with Mr. Harper.

But Mr. Trudeau’s election last year signaled a shift in policy that was welcomed by the White House. Mr. Trudeau did not criticize Mr. Obama’s rejection of the pipeline, and Mr. Trudeau has pledged to pursue an ambitious environmental agenda to coincide with Mr. Obama’s policies.

In December, Canadian officials helped to push through a historic global climate agreement in Paris.

“The climate relationship with Canada really just ramped up dramatically quickly,” Todd Stern, Mr. Obama’s special envoy for climate change, told reporters before Mr. Trudeau’s arrival.

The two leaders will meet privately on Thursday to discuss military cooperation, efforts to combat terrorism, improvements in trade and environmental concerns.

Among the issues the two leaders will seek to resolve is a decades-old dispute over softwood lumber. American officials say lumber from Canada is unfairly subsidized by the government there, an assertion that Canadian officials reject.

“That’s a longstanding and complicated issue, but we do welcome the Trudeau’s government interest in discussing a new arrangement for softwood lumber, and we’re open to exploring all options with Canada to address this important trade issue,” said Mark Feierstein, the senior director for the Western Hemisphere at the National Security Council.

But the most anticipated topic is the environment.

“Prime Minister Trudeau is already showing serious, concrete commitment to accelerating progress on climate,” Mr. Stern said. “The commitment of both leaders to addressing this global challenge is clear. And I suspect under their leadership, North America will make significant progress this year and next.”

The Obama administration wants to cut methane emissions from the oil and gas sector by 40 percent to 45 percent from 2012 levels by 2025. The Interior Department has proposed a number of regulations on methane leaks, but it has yet to write a regulation governing such leaks from current oil and gas drilling on public land.