“There is no way to ramp up U.S. L.N.G. exports and deliver on the imperative climate commitments that the U.S. and E.U. have pledged,” said Abigail Dillen, the president of Earthjustice, an environmental law organization. She warned that the buildup of L.N.G. infrastructure would “lock in expensive fossil dependence and dangerous pollution for decades to come.”

American and European officials also agreed to seek ways to decrease greenhouse gas emissions from L.N.G. infrastructure and pipelines and to reduce the release of methane from gas operations. They said they would ramp up energy efficiency initiatives, such as the deployment of heat pumps and the use of clean hydrogen technologies to displace fossil fuels, as well as expedite planning and approval of renewable energy projects such as offshore wind and solar power.

The Biden administration has banned Russian energy imports as part of a set of sanctions against Mr. Putin, a relatively easy step for the United States because it is a net exporter of energy. Some U.S. lawmakers would like the European Union to stop buying oil and gas from Russia altogether, but the prospect for that has been dismissed by several E.U. leaders, who see it as a financially disastrous step that would hurt Europe more than Russia.

Some energy experts said a further escalation of the war, such as a decision by Mr. Putin to use chemical, biological or nuclear weapons, could leave the European Union with little choice but to bar the purchase of Russian energy.

“We want as Europeans to diversify away from Russia, toward suppliers that we trust, that are friends and that are reliable,” Ms. von der Leyen of the European Commission said at the announcement with Mr. Biden. “Therefore the U.S. commitment to provide the European Union with an additional at least 15 billion cubic meters of L.N.G. this year is a big step in this direction, because this will replace the L.N.G. supply we currently receive from Russia.”

Still, oil and gas executives said Mr. Biden and Ms. von der Leyen would have to be patient and recognize that decisions on who sold gas to whom would be made across negotiating tables by private companies, not by politicians. Ultimately, exporters will seek to sell their gas to buyers willing to pay the highest price.

“This is a capitalist system,” Mr. Souki, the Tellurian executive, said. “It’s people like me who make those decisions. The government can’t tell us where to send the gas.”

Reporting was contributed by Matina Stevis-Gridneff, Christopher F. Schuetze, Monika Pronczuk and Zolan Kanno-Youngs.