Ukrainian soldiers check their weapons at a position on the front line in Donetsk, Russia, October 24, 2022 (AFP)

The United States is running low on several sophisticated weapons and munition to send to Ukraine in the midst of the ongoing war, CNN reported on Thursday citing three US officials familiar with the matter.

One of the officials said the stockpiles of certain systems were "dwindling" after Washington spent the past nine months supplying Ukraine with arms against Russia due to there being a "finite amount" of available stocks in the US arsenal that it is able to send, the report said.

The United States, the sources said, is mainly concerned about meeting Ukraine's demands for 155mm artillery ammunition and man-portable Stinger anti-aircraft missiles.

Meanwhile, some of the sources told CNN that there was concern regarding the US ability to produce additional weapons systems that Ukraine is demanding, such as the HARMs anti-radiation missiles, GLMRS SSM, and the shoulder-mounted Javelin anti-tank missiles, which Kiev has been highly reliant on since the beginning of the war.

White House National Security adviser Jake Sullivan said Tuesday that the United States and its allies would continue supporting Ukraine in terms of air defense supplies in light of the renewed Russian missile strikes on the country earlier in the week.

"The United States and our allies and partners will continue to provide Ukraine with what it needs to defend itself, including air defense systems," Sullivan said in a press release. "We will stand with Ukraine for as long as it takes."

Earlier that day, Ukrainian President Volodymyr Zelensky said that Russia launched 85 missile strikes that mostly targeted energy facilities, claiming that around 20 more strikes were expected.

The US Defense Department has said that it provided National Advanced Surface-to-Air Missile Systems (NASAMS) to Ukraine earlier this month, saying they were already operational.

The NASAMS is a short-to-medium-range ground-based air defense system that can be used against helicopters, cruise missiles, and aircraft.

Amid its confrontation with Russia, the US has given Ukraine a total of 8 NASAMS systems. According to authorities from the Pentagon, the delivery of the remaining six air defense systems is not anticipated to happen anytime soon.

The Biden administration approved another $400 million security assistance package for Ukraine last week that includes missiles for HAWK air defense systems, four Avenger air defense systems, and 192 Stinger missiles.

"Some of the capabilities include funding to refurbish Hawk air defense missiles for inclusion in future presidential drawdown packages, 45 refurbished T-72 tanks with advanced optics, communications, and armor packages, 1,100 Phoenix Ghost tactical unmanned aerial systems, 40 armored Riverine boats, and funding to refurbish 250 M1117 armored security vehicles," US Department of Defense spokesperson Sabrina Singh said.

The United States announced on October 28 a $275 million military assistance package for Ukraine, including HIMARS launchers, ammunition, and 155mm artillery rounds; two NASAMS (National Advanced Surface-to-Air Missile Systems) were also to be delivered to Ukrainian soldiers once they complete their training on the systems.

Amid signs of dwindling military support, House Democratic Caucus Chairman Hakeem Jeffries said earlier in the week that Congress would likely include aid to Ukraine as part of its bid to fund the government in Kiev and avid a shutdown before December 16.

"It is certainly the case that we have to make sure we arrive at a year-end spending agreement to continue to fund the priorities of the American people," Jeffries said during a press conference. "I expect that additional funding for Ukraine will be part of any year-end agreement."