The Biden administration prepared a $200 million package of additional military assistance for Ukraine in recent weeks but held off on delivering the aid despite appeals from Kyiv and some lawmakers, according to three people familiar with the issue.

A source familiar with the matter, however, said there are a number of other options on the table for further assistance to Ukraine, including a much larger package of aid that would be approved in the event of further incursion by Russia.

Earlier this week, National Security Adviser Jake Sullivan told reporters President Joe Biden told Russian President Vladimir Putin that if Russia launched an attack the U.S. would impose tough sanctions on Moscow and would send more military aid to Ukraine.

“We would provide additional defensive materiel to the Ukrainians above and beyond that which we are already providing,” Sullivan said, recounting Biden’s conversation with Putin.

The source familiar with the matter said Sullivan was referring to this much larger package of potential aid, not the $200 million shipment.

The administration's delay of the smaller shipment of weapons and military equipment was designed to give more time for diplomatic efforts to defuse tensions and to retain leverage in the case of a Russian attack on Ukraine, the three people familiar with the issue told NBC News.

The smaller package “has been on the president’s desk for roughly three to four weeks,” said one of the sources briefed on the issue.

The smaller, $200 million package was expected to be approved and announced last week but instead the White House chose to postpone any final decision, the sources said.

Although it’s unclear what the proposed $200 million aid package includes, Ukraine has asked for air defense systems, anti-ship missiles, more Javelin anti-tank missiles, electronic jamming gear, radar systems, ammunition, upgraded artillery munitions and medical supplies, according to two people familiar with the request.

After having submitted their urgent request for military assistance a month ago and received a positive response, the Ukrainian government was puzzled as to why the aid package had not gone ahead as expected. “There is slight frustration over this,” said a person familiar with the Kyiv government’s view.

The White House did not respond to a request for comment. A spokesperson for Ukrainian President Volodymyr Zelenskyy declined to comment.

A bipartisan group of 22 House lawmakers wrote a letter to Biden on Wednesday urging the administration to speed up military help to Ukraine.

“To maximize deterrence, it is critical that at least some military aid — Stingers, Javelins, drones, and anti-ship missiles — are provided immediately. The Ukrainian state must be equipped with the tools necessary to defend itself and the region against Russian aggression,” the lawmakers wrote.

In a commentary published Friday in Foreign Affairs, Ukraine’s foreign minister, Dmytro Kuleba, said it was vital “to deepen military assistance to Ukraine.”

“We have our own capable military forces in Ukraine, and we don’t expect Western countries to put boots on the ground," Kuleba wrote. “We do, however, need more weapons to be able to defend ourselves. Everything counts, from ammunition to medical equipment, but we are in particular need of air and missile defenses."

Kuleba said only firm resolve from the United States and NATO would succeed in countering Russia.

“For too long, the West has declined to take Putin’s ambitions seriously and responded with delay, indecision, and weakness. It is time to meet them with strength.”