The United States says it has provided Ukraine with its long-sought long-range missiles capable of precision strikes, and they have already arrived in the country.

White House National Security Advisor Jake Sullivan told reporters on Wednesday the US has delivered the Army Tactical Missile Systems, or ATACMS, to Ukraine. He also said the US will send more.

The US administration says that the military aid to cover the missile shipments was arranged by cutting costs in its existing budget.

Observers say attention is now focused on how Ukraine's access to the long-range missiles will affect the conflict.

Last year, the US provided mid-range missiles with a range of about 160 kilometers. US media reported that the new missiles give Ukraine nearly double that striking distance, up to 300 kilometers.

The Institute for the Study of War, a US think tank, said on Wednesday, "The arrival of long-range ATACMS missiles in sufficient quantities will allow Ukrainian forces to degrade Russian logistics and threaten Russian airfields in deep rear areas."