President Biden has agreed to send a small number of long-range missiles to Ukraine to bolster Ukrainian President Volodymyr Zelenskyy's war effort against Russia, Fox News has confirmed.

The president made the offer during his meeting with Zelenskyy Thursday, U.S. officials said. Information about number, type and date of delivery was not disclosed so as not to undermine Ukraine's use of the weapons. 

The White House and National Security Council declined to comment. 

Biden earlier had announced a $325 million security assistance package for Ukraine after he met with Zelenskyy, who visited the Capitol Thursday for the second time since Russia invaded his country in February 2022.

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President Biden Welcomes Ukrainian President Zelensky To The White House

Ukrainian President Volodymyr Zelenskyy walks with President Biden down the colonnade to the Oval Office during a visit to the White House Sept. 21, 2023. (Evan Vucci-Pool/Getty Images)

Capping his visit, which included meetings and discussions with lawmakers and Pentagon officials, Zelenskyy met with Biden at the White House before the $325 million plan was unveiled.

According to the U.S. Department of Defense, the package includes antitank weapons, air defense equipment, artillery rounds and other equipment to help meet Ukraine’s needs on the battlefield against Russia. Defense officials made no mention of long-range Army Tactical Missile Systems, ATACMS, being included. 

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ATACMS missile systems

In this handout photo released by the South Korean Defense Ministry, a U.S. Army Tactical Missile System (ATACMS) fires a missile into the East Sea during a South Korea-U.S. joint missile drill aimed to counter North Korea's ICBM test July 29, 2017, in East Coast, South Korea.  (South Korean Defense Ministry via Getty Images))

Ukraine has for months requested long-range missiles from the U.S., which would enable strikes on targets as far as 180 miles, making vulnerable Russian supply lines and other military targets behind the front lines. 

However, U.S. officials have expressed hesitancy to hand over the powerful weapons to Ukraine for fear it would escalate the war and provoke Russia. Last year, Russian Foreign Minister Maria Zakharova said Washington would cross a "red line" by providing Ukraine with long-range missiles, warning that Moscow "reserves the right to defend its territory."

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Zelenskyy and Biden

President Biden and first lady Jill Biden welcome Ukrainian President Volodymyr Zelenskyy and his wife Olena Zelenska on the South Lawn of the White House in Washington Thursday, Sept. 21, 2023.  (AP Photo/Susan Walsh)

High-level U.S. officials also said that ATACMS reduce the capability of the artillery the U.S. has already provided to Ukraine, known as HIMARS. HIMARS can shoot six missiles at a time, but if they are re-equipped to fire ATACMS, they can only shoot one missile at a time, officials said.

National Security Council spokesman John Kirby said Wednesday there were no plans to send ATACMS to Ukraine. That was true at the time, but Fox News has since learned BIden made the decision close to the time of his meeting with Zelenskyy on Thursday and then made the offer.

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Before heading into a closed-door meeting with Biden, Zelenskyy said he was there to "strengthen Ukraine’s position to defend our children, our families, our homes, freedom and democracy in the world."

"It's good that our countries are really, truly allies," he said.

Fox News' Caitlin McFall and Greg Wehner contributed to this report.