(Bloomberg) -- The Biden administration is growing even more frustrated with both congressional Republicans and allies in Europe over delays in funding Ukraine’s fight against Russia, people familiar with the matter said, as concerns mount that Russian forces could make major gains in the coming weeks.

There is no “Plan B” for the US to help Ukraine aside from the $60 billion in military aid that remains tied up in Congress, according to US officials who asked not to be identified discussing private deliberations. And European leaders need to get over delays and use profits from blocked sovereign Russian assets to help President Volodymyr Zelenskiy’s government, one of the people said.

European nations should also urgently respond to Ukrainian requests to provide the country with more Patriot air-defense systems from their own stocks, another person said.

A National Security Council spokesperson said Congress must act. Last month, National Security Adviser Jake Sullivan said “I don’t think we need to speak today about plan B” and that congressional approval had already taken too long.

Ukraine has been rationing its artillery shells in anticipation it might run out, General Christopher Cavoli, the head of European Command, told the House Armed Services Committee on Wednesday. Ukrainians are “outshot” by the Russian side 5 to 1 and that ratio will go to 10 to 1 in a “matter of weeks,” Cavoli said.

“Based on my experience in 37-plus years in the U.S. military, if one side can shoot and the other side can’t shoot back, the side that can’t shoot back loses,” he said. “So the stakes are very high.”

The allies’ most immediate worry is whether Ukraine will continue to be able to defend its airspace. Sensing Ukraine’s moment of weakness, Russia has been pounding the country’s critical infrastructure, inflicting some of the worst damage on it in over two years of war. 

The US has been pushing the Group of Seven to use the profits generated from $280 billion in blocked sovereign assets to raise more money quickly, for example by using them to issue bonds to help Ukraine. But several European Union states, including France and Germany, have so far opposed such a move.

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