WASHINGTON — President Joe Biden gathered other world powers Tuesday to coordinate on Ukraine as it battles Russia in a war now almost 20 months long — a deliberate show of U.S. support at a time when the future of its aid is entangled with a volatile faction of House Republicans who want to cut off money to Kyiv.

The phone call — convened by the United States and joined by key allies in Europe as well as the leaders of Canada and Japan — was held three days after Biden signed legislation hastily sent to him by Congress that kept the federal government funded but left off billions in funding for Ukraine’s war effort that the White House had vigorously backed.

All the countries that participated in the call stressed that their backing of Ukraine is unchanged, and no one questioned whether U.S. support of Kyiv was in doubt, according to the White House. But the administration warned Tuesday that Congress must not let the flow of aid be disrupted, lest Russian President Vladimir Putin exploit any lapses to his advantage.

“Time is not our friend,” said John Kirby, the spokesman for the National Security Council at the White House. He warned that any gaps in U.S. support “will make Putin believe he can wait us out.”

Kirby said the current tranche of congressionally-approved U.S. aid would be enough to help Ukraine for another “couple of weeks” or a “couple of months,” although the precise estimate would hinge on battlefield conditions.

The outlook for the future of Ukraine aid has been murky at best after Biden on Saturday signed a bill to fund U.S. government operations through mid-November that ignored the billions in additional funds for Kyiv requested by Biden in late August.

Kirby emphasized that House GOP leaders support Ukraine aid.

In Poland, President Andrzej Duda said after the call that Biden had assured the group of continued U.S. support for Ukraine and expressed strong conviction that Congress would not walk away.

“He assured us that there is backing for the continuing support for Ukraine, first of all for the military support,” Duda said in Kielce, Poland. “He said that he will get that backing in the Congress.”

Meanwhile, Ukraine, Poland and Lithuania have agreed on a plan they hope will help expedite Ukrainian grain exports, officials said, with needy countries beyond Europe potentially benefiting.

The deal means that grain inspections will shift from the Ukraine-Poland border to a Lithuanian port on the Baltic Sea, according to a statement from the Ukrainian farm ministry.

The move seeks to facilitate the transit of Ukrainian exports through Polish territory, the statement said.

From the Lithuanian port of Klaipeda, where inspections for pests and plant diseases will take place from Wednesday, the grain can be exported by sea around the world.