US likely to send long-range ATACMS missiles to Ukraine for the first time: Officials

"They are coming," one U.S. official told ABC News.

The Biden administration is likely to send Ukraine long-range Army Tactical Missile Systems, or ATACMS, to help in its fight to repel the Russian invasion of its territory, according to U.S. officials.

"They are coming," said one official who had access to security assistance plans. The official noted that, as always, such plans are subject to change until officially announced.

A second official said the missiles are "on the table" and likely to be included in an upcoming security assistance package, adding that a final decision has not been made. It could be months before Ukraine receives the missiles, according to the official.

But pressed on the matter by ABC News, White House spokesman John Kirby said a decision hasn't been made.

"There's no decision on ATACMS right now," Kirby said during the interview, in New Delhi, India.

"As the president has said, they're not off the table," Kirby added. "We continue to discuss the viability of ATACMS."

With a range of up to 190 miles, depending on the version, deploying ATACMS could allow Ukraine to reach targets nearly four times further away than with the currently-provided rockets for its U.S.-made High Mobility Artillery Rocket Systems and M270 multiple-launch rocket systems.

The administration has until now rejected Ukrainian President Volodymyr Zelenskyy's requests for the weapons, even after the United Kingdom and France have sent comparable Storm Shadow missiles, due to concerns both over escalation with Russia and of maintaining America's own stockpiles.

In July of 2022, National Security Adviser Jake Sullivan said the U.S. was "prepared to take risk," but implied that sending ATACMS could lead to direct conflict with Russia.

"There are certain capabilities the president has said he is not prepared to provide. One of them is long-range missiles, ATACMS, that have a range of 300 kilometers, because he does believe that while a key goal of the United States is to do the needful to support and defend Ukraine, another key goal is to ensure that we do not end up in a circumstance where we are heading down the road towards a third world war," he said at the Aspen Security Forum.

One year later at the same event, Sullivan was less definitive.

"Whether or not we ultimately give ATACMS will be a decision for the president. He has spoken with President Zelenskyy about it. They continue to have that conversation," he said this July.

The Biden administration has taken an incremental approach with the types of weapons it has sent to Ukraine since the invasion, ramping up from handheld launchers, to sophisticated air-defense platforms, to armored vehicles, and reversing earlier decisions not to send Abrams tanks or to train Ukrainians on advanced F-16 fighters.

With Ukrainian forces struggling to break through heavily-defended Russian lines more than expected in its ongoing counteroffensive, political pressure in Washington over sending military aid has increased -- along with a desire to see more progress on the battlefield.

A surprising discovery could also ease the administration's choice to send the weapons: The U.S. has found it has more ATACMS in its inventory than originally assessed, the two officials told ABC News.

The serviceability of the rediscovered stockpile is not yet clear, nor which specific type of missiles it contains. ATACMS come in several forms, from missiles with large high-explosive warheads, to anti-personnel cluster-munition versions that drop hundreds of bomblets on targets.

In addition to giving Ukrainian crews much greater standoff distance when striking Russian positions -- making it more difficult for the Russians to fire back -- ATACMS could also help Ukraine more easily reach targets in Crimea.

"I think specific targets in Crimea would be command and control, logistics hubs -- especially ammunition facilities -- and air bases," said Mick Mulroy, an ABC News contributor who served as a CIA officer and deputy assistant secretary of defense.

The U.S. has committed more than $43.7 billion in security aid to Ukraine since the beginning of the invasion in February 2022.

ABC News' Ben Gittleson contributed to this report.