A US Defense Department spokesperson says the US military has begun training Ukrainians to use and maintain the Patriot missile defense system.
Air Force Brigadier General Pat Ryder told reporters on Tuesday that "upwards of 90 to 100 Ukrainians" will train for several months at an army base in Oklahoma.
The United States earlier decided to offer the Patriot system to Ukraine to strengthen the country's air defense against Russian missiles.
The US-produced Patriot is a mobile surface-to-air missile system designed to intercept ballistic and cruise missiles, as well as aircraft.
The Dutch defense ministry on Tuesday said it was also ready to provide Ukraine with the Patriot system.
Dutch Prime Minister Mark Rutte reportedly conveyed the idea to US President Joe Biden at the White House on Tuesday.
In a Twitter post, Dutch Defence Minister Kajsa Ollongren referred to a deadly missile strike on an apartment building in the eastern Ukrainian city of Dnipro on Saturday.
She wrote it is crucial that Ukraine become capable of defending itself, and that the Netherlands is discussing the provision of the Patriot system with the US and Germany.
Ukraine's air force has suggested that Dnipro was struck by a Russian anti-ship missile.
It said such missiles can only be shot down with surface-to-air missile systems like the Patriot.