At a March 10 news conference at the White House, President Obama said the Republican Party establishment is to blame for the divisive tone of the 2016 presidential race. (The White House)

President Obama said Thursday that he is not responsible for the Republican Party’s “crackup” even though some GOP leaders have blamed him for Donald Trump’s divisive-but-effective campaign for the party’s presidential nomination.

“I have been blamed by Republicans for a lot of things, but being blamed for their primaries and who they’re selecting for their party is novel,” he said during a joint news conference with visiting Canadian Prime Minister Justin Trudeau.

The president instead pointed a finger at the Republican Party leaders who “have been feeding the Republican base for the last seven years a notion that everything I do is to be opposed” and “that cooperation or compromise somehow is a betrayal, that maximalist, absolutist positions on issues are politically advantageous.”

Obama said that “ultimately I want an effective Republican Party” that would be “prepared to govern, whether in the minority or the majority, whether in the White House or not.” He said such a party could “challenge some of the blind spots and dogmas in the Democratic Party. I think that’s useful.”

But he said he was not responsible for the “circus” playing out in the GOP primaries.

Canadian Prime Minister Justin Trudeau arrived in Washington for the White House state dinner, and Twitter users remarked on the "bromance" friendship between Trudeau and President Obama. (Victoria Walker/The Washington Post)

Obama and Trudeau also addressed bilateral issues. They announced they would seek a 40 percent to 45 percent reduction in methane emissions below 2012 levels by the oil and gas industry by 2025, and, to meet that commitment, both governments said they would regulate emissions from existing sources, not just new wells.

The Environmental Protection Agency will begin drafting regulations immediately, according to a joint statement from the two leaders.

The oil and gas industry is the single largest industrial source of methane emissions in the United States and globally. Mark Brownstein, vice president of climate and energy at the Environmental Defense Fund, said that, if adopted, the proposed cut in emissions of methane, a potent greenhouse gas, worldwide would be like closing a third of the world’s coal plants.

“This is arguably the single biggest, most impactful, most immediate thing we can do to slow the rate of warming right now,” Brownstein said.

Obama and Trudeau also pledged to safeguard the Arctic with a series of initiatives that will protect more than 10 percent of the marine areas, designate shipping corridors with low environmental impact, and establish new offshore oil and gas leasing plans, White House officials said.

The focus on the Arctic reflects both a shared sense of alarm about growing signs of climate change in the region and the fruits of Trudeau’s victory last fall over the previous Conservative Party prime minister, Stephen Harper.

The change in the relationship was clear Thursday morning when Trudeau and his wife, Sophie, arrived on the South Lawn, where a welcoming group was gathered.

“It’s long been said that you can choose your friends, but you cannot choose your neighbors,” Obama joked. “We are very proud to welcome the first official visit by a Canadian prime minister in nearly 20 years.” Then, appropriating a peculiarly Canadian figure of speech, he added to laughter, “It’s about time, eh?”

“With this partnership, the U.S. and Canada are charting a new, ambitious vision for Arctic conservation and putting in place concrete mechanisms to drive future progress,” Brian Deese, a senior adviser to the president, said in an earlier interview promoting the attention paid to Arctic issues.

“The fact that this is being raised at the highest levels shows that both countries recognize the Arctic is a real, emerging priority,” Gerald Butts, senior political adviser to Trudeau, said in a statement.

U.S. officials said that the enhanced collaboration between the United States and Canada will spur other Arctic nations to match these commitments but that agreements on the Arctic must include a wide array of nations, including Russia, Denmark and Norway.

The U.S.-Canada pledge to expand protected areas in the Arctic reflects a recent push by Obama and Trudeau to put some areas of the Arctic off-limits to development at a time when they are becoming more accessible to commercial exploitation and shipping, activities that bring with them risks of underwater noise, black-carbon pollution, collisions and potential oil spills.

Trudeau came into office promising to protect 5 percent of Canadian waters by the end of next year — less than 1 percent are protected now — and 10 percent by 2020. One of the key areas under consideration is the northern part of Ellesmere Island, which, along with the northern part of Greenland, is poised to be the last place with summer sea ice as the planet warms. It is largely uninhabited, and there is no shipping there because the ice is too thick.

“Canada has a lot of catching up to do here, and also on the climate file, as they have dragged their feet for decades,” said Dalhousie University marine biology professor Boris Worm in an email. “But Trudeau seems determined to do it. The question is: How?”

On the U.S. side, environmentalists have lobbied the administration to ban all oil and gas exploration in the Arctic — something Obama has resisted — and have pushed for even greater protections in specific parts of the Chukchi and Beaufort seas.

For example, Barrow Canyon is a deep, 150-mile-long underwater trench that straddles the Chukchi and Beaufort seas. Between the movement of sea ice and ocean mixing, it represents a foraging hot spot for a range of species including seabirds and bowhead whales, according to the Pew Charitable Trusts.

The Beaufort Sea is particularly sensitive to shipping, too.

Another marine area that could qualify for new protection in the U.S. Arctic would be the western Aleutian islands, and groups such as the Sierra Club are pushing the president to declare the Arctic National Wildlife Refuge a national monument.

On methane emissions, EPA Administrator Gina McCarthy said the agency was asking oil and gas companies to provide data on emissions from existing wells. But the industry is expected to oppose new regulations on those sites.

“New regulations to address existing wells are really unnecessary window dressing, as industry is already reducing methane dramatically,” said Frank Maisano, an energy policy expert at Bracewell, a law and lobbying firm. “Industry has been ahead of the curve on this for years, working diligently on its own to reduce methane emissions,” which he said made good business and environmental sense.

Sandra Snyder, a lawyer at Bracewell, said compliance with EPA rules on existing wells would be a burden, adding that “all of this imposes an additional strain on an industry that is struggling under low oil and gas prices.”

But Brownstein said that the “industry response has been underwhelming, and we basically have to do something.”