US struggles to rush weapons to Ukraine before Trump takes office

A Biden administration push to send billions of dollars of military equipment to Ukraine before it leaves office is facing major logistical hurdles and is raising concern that the transfers will deplete already-stretched U.S. stockpiles, officials said.

The impediments underscore how much Donald Trump’s election has disrupted the U.S.-led campaign to aid Ukraine, which has suffered severe battlefield setbacks in its war against Russia and is now grappling with the future of the Western arms pipeline that has enabled it to keep fighting.

More than $7 billion in drawdown authority allowing the Pentagon to transfer weapons and munitions to Ukraine from its stocks remains unspent, along with over $2 billion to fund long-term equipment contracts for Kyiv.

Trump has vowed to end the war in Ukraine before taking office. While the president-elect hasn’t spelled out a plan for doing so, Biden administration officials fear that the incoming administration will curtail Ukraine arms shipments as part of an effort to lead Kyiv and Moscow to the negotiating table.

By funneling as much military aid to Kyiv as it can before January, Biden administration officials are hoping to give Ukraine a stronger negotiating position and bolster its defenses. Before the election, the administration had been aiming to deliver the remaining aid to Ukraine by April, according to a Pentagon official.

That timeline has taken on new urgency since the election.

In response to stepped-up Russian drone and missile attacks, the Pentagon is sending to Ukraine more than 500 interceptors for the Patriot missile defense system and the National Advanced Surface-to-Air Missile System, or NASAMS, which are expected to arrive in the weeks ahead, according to a senior administration official.

Those shipments should meet Ukraine’s air defense needs for the rest of this year, said one U.S. official.

On Friday, the administration said it would send “a small number of contractors” to help Ukraine repair and maintain F-16s and other systems, the Pentagon official said. The contractors will arrive in the coming months and will work far from the front lines.

As recently as August, the Biden administration rejected such a move, but since then more systems became inoperable because of a lack of skilled workers to repair or maintain them.

“Ensuring these weapon systems remain mission capable is critical for Ukraine’s defense against Russian aggression,” the Pentagon said in a statement.

Weapons deliveries to Ukraine typically take weeks or even months, and the impact of the planned increase in weapons transfers on U.S. military stockpiles, particularly air defenses, is “a big concern,” said another senior U.S. official. The U.S. is looking at options such as buying back weapons from other countries to give to Ukraine, the senior U.S. official said.

Ukrainian officials have pressed for additional Army Tactical Missile Systems, or ATACMS, which have a range of up to 200 miles, saying they would enable strikes far behind Russian front lines.

The Pentagon has been reluctant to send additional ATACMS, arguing Russia has moved aircraft and other valuable targets out of range. The Biden administration has refused to let Ukrainian forces use the missiles to strike into Russia itself.

Defense Secretary Lloyd Austin refused a recent request from President Volodymyr Zelensky to give priority to delivery of Ukraine’s ATACMS over other buyers, according to two U.S. officials and an adviser to the Ukrainian government. Breaking longstanding agreements with other customers would be “a lot to ask,” Austin told Zelensky, according to one of the officials.

A new version of the weapon, called the Precision Strike Missile, is under production but will take years to make in large enough numbers to replace the ATACMS, another of the officials said.

The administration is asking allies to send Ukraine missiles from their stockpiles, the first U.S. official said.

The Pentagon also has limited stores of air-launched munitions it can send to arm Ukraine’s new F-16 jet fighters, according to the senior U.S. official and a former Defense Department official briefed on the discussions. Kyiv’s forces are using the planes primarily in an air-defense role to help shoot down Russian missiles and drones.

The Pentagon has been sending AGM-88E Advanced Anti-Radiation Guided Missiles, which are air-to-ground missiles designed to home in on enemy radars such as those used by surface-to-air missiles; advanced medium-range air-to-air missiles, which can be launched from F-16s as well as from NASAMS; and Joint Direct Attack Munition kits, which convert unguided bombs to smart weapons for attacking ground targets.

Alexander Ward contributed to this article.

Write to Lara Seligman at lara.seligman@wsj.com, Nancy A. Youssef at nancy.youssef@wsj.com and Gordon Lubold at gordon.lubold@wsj.com