Ukraine has long sought these sophisticated fighter jets so as to better fight the Russian invasion, and is now engaged in a fitful counter-offensive aimed at retaking land held by Russian forces.

The US training will involve "several" pilots and "dozens" of personnel to maintain the aircraft, said Pentagon spokesman Pat Ryder.

"These pilots will be conducting English language training at Lackland Air Force Base in San Antonio, Texas in September prior to attending F-16 flying training in Arizona" the following month, he said.

The Arizona training will take place at Morris Air National Guard Base, he added.

President Joe Biden and his Ukrainian counterpart Volodymyr Zelensky spoke Thursday and discussed the training program, the White House said.

"President Biden reiterated the US commitment to support Ukraine's defense against Russian aggression for as long as it takes, and to hold Russia accountable for its actions," a White House statement said.

The US program expands plans already announced by European allies to train Ukrainian personnel to fly the US-made F-16.

Last week the United States told Denmark and the Netherlands they can transfer their F-16s to Ukraine when the country's pilots are trained to use them.

On Thursday, Norway said it too would give F-16s to Ukraine, with news agency NTB reporting the donation would be between five and 10 planes.

Ryder said the training would normally last from five to eight months, depending on the skills the pilots already possess.

Language training at the beginning was crucial, "given the complexities and the specialized English that's required to fly these aircraft," he said.

The US is moving ahead with its own training program in recognition that Denmark and the Netherlands could not handle all the pilot preparation that Ukraine needs, Ryder added.

"We know that as the Danes and the Dutch prepare to train those pilots, that at a certain point in the future, capacity will be reached," he said.