The Kremlin said Thursday that Ukraine's access to long-range weapons, including ATACMS provided by the United States, would not fundamentally change the outcome of the conflict, now in its third year.

That comments came hours after the State Department said the United States had secretly sent ATACMS missiles to Ukraine for use inside its own territory, and that the weapons had arrived this month.

"The United States is directly involved in this conflict. It is on the road to increasing the range of the weapons systems it already supplies," Kremlin spokesman Dmitry Peskov told reporters.

"This will not fundamentally change the outcome of the special military operation. We will get our way. But it will cause more problems for Ukraine itself," Peskov added.

Some ATACMS missiles can hit targets up to 300 kilometres (190 miles) away, and a Defense Department spokesperson confirmed that was the long-range variant supplied to Ukraine.

The details on ATACMS came on the same day US President Joe Biden signed a bill to provide $61 billion in new aid for Ukraine, clearing the way for the Pentagon to announce an assistance package featuring desperately needed artillery and air defence munitions.