President Donald Trump and Prime Minister Justin Trudeau of Canada voiced commitments to work together on a range of issues at a meeting Monday at the White House, from trade to border security. But they gave no indication that the two leaders talked about climate change.

Last year, Trudeau and then-President Barack Obama agreed on a goal of cutting emissions of methane, a potent greenhouse gas, by 40 to 45 percent by 2025. The pledge came as part of a larger set of commitments on energy and Arctic policy.

Obama said at the time that the two countries were "responsible for a lot of the carbon pollution that is causing climate change. If we don't agree, if we're not aggressive, if we're not far-sighted, if we don't pool our resources around the research, and development and clean energy agenda required to solve this problem, then other countries won't step up and it won't get solved."

The joint statement issued by Trump and Trudeau on Monday did include a mention of the two countries' collaboration "in the clean energy sphere," but made no reference to methane or the March agreement. Also left unspoken was a joint pledge announced in June by the U.S., Canada and Mexico to work towards developing at least half the continent's electricity from carbon-free sources, including nuclear, by 2025. The pact relied on Obama's successor staying committed.

Trudeau has come under pressure at home for his mixed policies on climate change. He has proposed a national carbon tax and has pledged that the country will meet its commitment to the Paris climate agreement to cut emissions 30 percent below 2005 levels by 2030. But he has also supported the country's oil and gas industry, particularly the carbon-intensive tar sands. Last year, his administration approved two pipelines that would expand exports of tar sands oil.

One potential area of cooperation for the two leaders is the Keystone XL pipeline, which would bring more tar sands oil into the U.S. Trudeau had signaled support for the pipeline, but his position was rendered moot when Obama rejected it largely because of its potential climate impact. Trump issued an executive order soon after taking office seeking to revive the project, and TransCanada, the company behind it, quickly submitted a new application.

Monday's joint statement made a passing, vague reference to the proposal. "As the process continues for the Keystone XL pipeline, we remain committed to moving forward on energy infrastructure projects that will create jobs while respecting the environment."