The HAWK interceptor missiles would be an upgrade to the Stinger missile systems – a smaller, shorter range air defence system – that the US has already sent to blunt Russia’s invasion.

The Biden administration would use the Presidential Drawdown Authority (PDA) to transfer the Hawk equipment which is based on Vietnam-era technology, but has been upgraded several times.

The PDA allows the US to transfer defence articles and services from stocks quickly without congressional approval in response to an emergency.

Reuters was unable to determine how many HAWK systems and missiles the US has available to transfer. The White House declined to comment.

The above is the predecessor to the Patriot missile defence system made by Raytheon Technologies, which remains off the table for Ukraine, US officials have told Reuters.

US president Joe Biden pledged to Ukrainian president Volodymyr Zelensky that Washington will provide Ukraine with advanced air systems after a devastating missile barrage from Russia earlier this month.

Nato secretary general Jens Stoltenberg has said that Spain intends to send four HAWK launchers.

The US will likely initially send interceptor missiles for the Hawk system to Ukraine because it was unclear if enough US launchers were in good repair, one US official told Reuters.

The US systems have been in storage for decades.

A PDA is being considered for later this week, US officials have said.

One US official said it would likely be about half the size of the recent security assistance packages which have been around US$700 million.

It was not immediately clear if Hawk interceptor missiles will be included. However, US officials have previously cautioned that size and composition of military aid packages can change rapidly.

Since the Feb 24 Russian invasion of neighbouring Ukraine, which Moscow calls a “special military operation”, the US has sent around US$17.6 billion worth of security assistance to Kyiv.