The weapons were part of a $300m (£240m) aid package approved by US President Joe Biden in March and they arrived this month.

They have already been used at least once to strike Russian targets in occupied Crimea, US media report.

Mr Biden has now signed a new $61bn package of aid for Ukraine.

The US previously supplied Ukraine with a mid-range version of the Army Tactical Missile Systems (ATACMS) but had been reluctant to send anything more powerful, partly over concerns about compromising US military readiness.

However, Mr Biden is said to have secretly given the green light to send the long-range system - which can fire missiles distances of up to 300km (186 miles) - in February.