Ukraine summoned the deputy head of the US embassy on Wednesday to warn him that any delay by the United States in providing military aid to Ukraine would embolden Russia, the Ukrainian Foreign Ministry said.

US media reports that among the weapons the US has suspended are Patriot air defense missiles, Hellfire precision artillery shells, and other missiles that Ukraine launches from F-16 fighter jets and drones.

A senior source in the Ukrainian military told AFP that without US ammunition, Ukraine would find it difficult to defend itself against Russian attacks.

"We are now seriously dependent on American arms supplies, although Europe is doing its best, but without American ammunition we will have a hard time," the source said.