President Biden spoke with his Ukrainian counterpart, Volodymyr Zelensky, on Wednesday as Poland cautioned that Biden’s plan to evade a Russian grain blockade by building silos at the Poland-Ukraine border could take three to four months to effect.

Biden told Zelensky he would send a new tranche of $1 billion in military aid to fight Russia’s nearly four-month-old invasion and an additional $225 million for humanitarian aid, according to the White House. Congress last month approved $40 billion to assist Kyiv in the conflict.

A readout of the call made no mention of Biden’s assertion Tuesday that NATO allies would help Ukraine export more than 20 million tons of grain by building storage facilities near western Ukraine.

The plan expounded by Biden would, in theory, bypass a Russian blockade of Ukraine’s Black Sea ports.

“We’re working on a plan to get it out through other countries by rail,” the president told delegates at the AFL-CIO’s annual conference in Philadelphia.

“But guess what? Ukraine has a system like Russia has — a rail gauge that is different than the gauge of the rest of the tracks in Europe,” Biden said. “So we’re going to build silos — temporary silos — in the borders of Ukraine, including in Poland, so we can transfer it from those cars into those silos, into cars in Europe, and get it out to the ocean, and get it across the world.”

Polish Agriculture Minister Henryk Kowalczyk wrote Wednesday on Facebook that “President Joe Biden’s statement about his intentions to build temporary silos in Poland on the border of Ukraine is a very interesting idea.”

The minister added, however, that “it should be noted that the realization of this type of investment takes about three to four months.”

Russia and Ukraine jointly supply about a fourth of the world’s wheat exports. The war has caused global food prices to increase and triggered concern about hunger in poorer countries otherwise far removed from the conflict.

The White House said Wednesday that Biden and Zelensky also discussed Russian attempts to seize all of the eastern Donbas region — where two pro-Moscow rebel states declared independence from Ukraine in 2014 — after Ukrainian troops in March beat back a Russian attempt to seize Kyiv and other northern areas.

Biden said the new military aid will include “additional artillery and coastal defense weapons, as well as ammunition for the artillery and advanced rocket systems that the Ukrainians need to support their defensive operations in the Donbas,” according to the White House.

Secretary of State Antony Blinken also spoke with his Ukrainian counterpart, Foreign Minister Dmytro Kuleba, on Wednesday about the arms shipments, as well as “efforts to ensure that Ukrainian agricultural products reach international markets,” according to a State Department release.