The meeting in Bonn, Germany, represents the first of two gatherings this week where international partners will pressure the increasingly recalcitrant United States to affirm its role in the agreement of more than 190 nations.

Other industrialized nations, such as China, France and Germany, each sent dozens of officials — the French delegation alone had 42 official participants. The United States sent 44 official participants just last year.

In Fairbanks, Alaska, on Thursday, the United States will host a ministerial of the eight-nation Arctic Council, an event sure to highlight rapid changes to the fastest warming part of the Earth.

In recent days, White House officials have taken an apparent turn away from remaining in the Paris climate agreement, with several administration officials arguing that the accord binds the Trump administration to the ambitious greenhouse gas reduction goal promised by the Obama administration, or something even stronger.

That interpretation is contested by many legal experts, however, as well as participants in past international climate negotiations.

“Having been intensely involved in such negotiations for a long time, there can be no doubt that Paris is utterly nonbinding, and therefore, each country is free to adjust their pledges in accordance with their own national circumstances,” said James Connaughton, who headed up the White House Council on Environmental Quality under President George W. Bush.

Meanwhile, a wave of international and domestic lobbying has intensified, with foreign allies and many corporations calling for the United States to stick with the deal, even as U.S. political conservatives push for a withdrawal — matching a similar tension between internationalists and conservatives within the White House itself.

“We strongly hope that the US will stay committed to the Paris Accord,” Francois Delattre, the French ambassador to the United Nations, said in an email to The Washington Post. “This is key in itself but also as an illustration of America’s commitment to world affairs.”

Delattre said he “underscored this point” in a White House lunch with Trump, when the president met with members of the U.N. Security Council late last month.

It has all set the stage for a potentially dramatic decision — precisely the type that Trump seems to enjoy making.

The Paris climate agreement, struck at U.N. talks in December 2015, joins the voluntary carbon-cutting pledges of more than 190 countries. The parties to the agreement are expected to increase their ambitions over time, with the goal of eventually setting the world on a course to limit global warming to “well below” a 2 degrees Celsius (3.6 degrees Fahrenheit) rise over temperatures seen in the late 1800s.

The Obama administration pledged to reduce U.S. greenhouse gas emissions by 26 to 28 percent below their 2005 levels by the year 2025 — less than 10 years from now. Yet even this ambitious pledge, combined with those of other nations, is not enough to keep the world within the 2-degree temperature limit, which is why increased ambition over time is central to the agreement.

The divide within the White House is between those, like Secretary of State Rex Tillerson and Energy Secretary Rick Perry, who would have the United States revise its commitment downward, and those like Environmental Protection Agency Administrator Scott Pruitt, who think simply remaining in the deal at all opens the Trump administration up to legal challenges to its domestic energy policies.

On Monday, 40 conservative organizations sent president Trump a letter “in enthusiastic support of your campaign commitments to withdraw fully from the Paris Climate Treaty and to stop all taxpayer funding of UN global warming programs.” The groups argue that the United States might consider withdrawing from the U.N. Framework Convention on Climate Change, a 1992 Senate-ratified treaty that is the foundation for subsequent U.N. climate deliberations, including the Paris agreement.

Meanwhile, Google, Apple and more than 20 other firms took out an ad in the New York Times on Monday throwing their support behind the agreement.

“By expanding markets for innovative clean technologies, the agreement generates jobs and economic growth,” the companies’ letter says. “U.S. companies are well positioned to lead in these markets. Withdrawing from the agreement will limit our access to them and could expose us to retaliatory measures.”

It is unclear how other nations would react if the United States were to withdraw from the deal, but “retaliatory measures” have certainly been mentioned in the past.

Nicolas Sarkozy, the former president of France, has even suggested “a carbon tax at Europe’s borders, a tax of 1 to 3 percent for all the products that come from the United States, if the United States exempts itself from the environmental regulations that we ourselves have imposed on our businesses.”

The United States, as the world’s second largest emitter, is central to the Paris accord, both symbolically and also mathematically. Indeed, the country lowering its emissions as promised by the Obama administration could determine whether the world itself is positioned to curb global warming significantly in coming years.

According to an analysis by the think tank Climate Interactive, the Paris agreement pledges would shift the world from a path in which global emissions are expected to rise significantly out to the year 2030 (as economies grow and populations boom), onto one in which emissions remain relatively flat over the next 13 years. That’s not enough to hit the 2 degrees Celsius goal, but it is enough to keep global warming at least somewhat under control.

However, the group found, 21 percent of that achievement — or about one-fifth of the emissions cuts — depend on the United States. Therefore, if the United States doesn’t hit its promise to the world under Barack Obama, global emissions will keep growing to 2030 at least (assuming other nations do not pitch in with far deeper cuts than proposed so far, deep enough to offset the United States’ failure to contribute).

Analysis of how different countries contribute to pledged greenhouse gas emissions reductions under the Paris climate agreement. (Climate Interactive)

“The United States is contributing 21 percent of the pledged global reductions in greenhouse gas emissions,” said Ellie Johnston, the climate and energy lead at Climate Interactive. “If the United States doesn’t follow through on its commitment, it will shift more of the burden of climate action to those countries who have polluted the least. It’s unfair by any measure.”