WASHINGTON, May 13 (Xinhua) -- One U.S. ally has pledged to send Ukraine one Patriot air defense system, U.S. National Security Advisor Jake Sullivan said on Monday.

Sullivan told a daily press briefing at the White House that he has been consulting with allies "every single day" on how to get more Patriot batteries, a type of advanced surface-to-air missile defense system, to Ukraine to bolster its air defense capabilities in the face of intensifying Russian airstrikes.

"And I think we recently had some good news from an ally about getting one in," Sullivan said, adding that President Joe Biden's administration is also looking for other systems from allies to equip the Ukrainian forces -- ones that the United States is able to resupply its allies to "backfill" their air defense needs.

As regards the number of Patriots the United States and its allies are now able to provide to Ukraine, Sullivan said "dozens of Patriot batteries I don't think is the right order of magnitude for what we're trying to get in there."

Biden approved 400 million U.S. dollars Friday in additional weapons aid to Ukraine using the presidential drawdown authority (PDA). Sullivan said another PDA package for Ukraine is expected "just in the coming days."

Ukraine has for months been requesting additional Patriots from the West, with officials saying the country needs a total of 26 such systems to cover the entirety of its territory and at least seven to protect key targets from Russian aerial bombardments.

U.S. Secretary of Defense Lloyd Austin said in late April that the United States was committed to supplying Ukraine with additional Patriots, but that in order to do so Washington would have to rely on help from its allies.

"I think going forward, we'll be able to hopefully work with a number of countries to put together additional Patriot capability," Austin told a Pentagon news conference at the time, seemingly suggesting that additional U.S. versions of system are not readily available for Kiev.