WASHINGTON/KYIV - US Secretary of Defense Lloyd Austin said on Friday the United States is committed to supplying Ukraine with additional Patriot air defense systems, and that in order to do so Washington will have to rely on help from its allies.

Austin made the remarks during a press conference at the Pentagon, which was held almost concurrently with an announcement from the department that the United States is sending a new weapons aid package to Ukraine worth $6 billion. That package, though, included only additional munitions for Patriots that were previously delivered.

Austin told reporters at the press conference that "it's left to be seen" how Ukraine would end up receiving more Patriots, which President Volodymyr Zelensky again asked for just a little while ago at a virtual Ukraine Defense Contact Group meeting, a US-led multilateral mechanism to discuss military support for Ukraine amid its conflict with Russia. The meeting convenes about once in a month.

I think going forward, we'll be able to hopefully work with a number of countries to put together additional Patriot capability ... It's not just Patriot that they need, they need other types of systems and interceptors as well.

Lloyd Austin, US Secretary of Defense

"I think going forward, we'll be able to hopefully work with a number of countries to put together additional Patriot capability," Austin said, seemingly suggesting that additional US versions of system are not readily available for Kyiv.

"It's not just Patriot that they need, they need other types of systems and interceptors as well," Austin said.

At the Ukraine Defense Contact Group meeting, Zelensky said his country needed at least seven Patriots or similar defense batteries to fend off Russian air strikes against Ukrainian cities.

ALSO READ: Biden vows quick provision of additional arms to Ukraine

"We urgently need Patriot systems and missiles for them," he said. "This is what can and should save lives right now."

In addition to missiles compatible with the Patriots, the $6 billion package that the Pentagon announced also included more munitions for the National Advanced Surface-to-Air Missile Systems, or NASAMS, and equipment to integrate Western air defense launchers, missiles, and radars with Ukraine's air defense systems.

The $6 billion package that the Pentagon announced also included more munitions for the National Advanced Surface-to-Air Missile Systems, or NASAMS, and equipment to integrate Western air defense launchers, missiles, and radars with Ukraine's air defense systems

These capabilities will be provided through the Ukraine Security Assistance Initiative (USAI), which authorizes President Joe Biden's administration to procure capabilities from US domestic weapons manufacturers as well as foreign partners. Weapons being supplied under the USAI framework takes a longer time to be built, thus an extended period - probably months or even years - to get to the hands of Ukrainian soldiers.

On Wednesday, the White House approved $1 billion in weapons and equipment through the Presidential Drawdown Authority, which, unlike the USAI, could realize a much faster delivery because capabilities sent through this route are those in the Department of Defense's storage.

It is thanks to a sweeping foreign aid package which the US Congress passed and Biden signed into law on Wednesday that the United States is able to funnel weapons into Ukraine on such a large scale. Of the legislation's $95 billion total, about $61 billion is for funding Ukraine's defense against Russia.

ALSO READ: Media: 2 killed in Zaporizhzhia by Ukrainian drone attack

Explosions heard across Ukraine

Separately, local media outlets reported that explosions were heard in several Ukrainian regions late on Friday amid Russian missile attacks.

In particular, blasts have rocked Ukraine's central Vinnytsia region and the western Ivano-Frankivsk region, the government-run Ukrinform news agency said.

Several explosions also rattled Ukraine's eastern city of Kharkiv, according to Mayor Ihor Terekhov.

The Ukrainian Air Force said on Telegram that Russia launched cruise missiles and aeroballistic missiles at Ukraine during the air strike.

READ MORE: Kremlin: Aid to Ukraine to make US richer, Ukraine poorer

Ukrainian Telegram channels warned that Russia was likely preparing a new missile attack on Ukraine as a group of Tu-95 strategic bombers had taken off from Olenya airfield in Russia's northwestern Murmansk region.