WASHINGTON, Sept 5 (Reuters) - U.S. President Joe

Biden's administration is engaged in urgent discussions with

Congress to allow it to use up $6 billion in military aid for

Ukraine before a Sept. 30 deadline, according to multiple

sources familiar with the matter.

The effort comes at a high-risk moment for Ukrainian forces,

who are advancing into Russia's Kursk region while trying to

hold off Russian forces threatening the eastern Ukrainian city

of Pokrovsk.

The Presidential Drawdown Authority (PDA), a key component

of a $61 billion aid package for Ukraine passed in April, allows

the president to transfer defense articles and services from

U.S. stocks in response to emergencies.

PDA has been the primary mechanism the Biden administration

has used to ship weapons to Ukraine. Most recently, the

administration announced on Aug. 23 a new military aid package

worth $125 million, including air-defense missiles,

counter-drone equipment, anti-armor missiles and ammunition.

However, most of the $7.8 billion in PDA in the bill Biden

signed into law in April has not been used, leaving officials

scrambling to find a way to keep the remaining $6 billion from

expiring as the Sept. 30 deadline - the end of the 2024 fiscal

year - approaches.

Sources close to the negotiations told Reuters that the

State Department hopes to attach an extension of the PDA

authorities to a Continuing Resolution, a short-term emergency

spending bill that the Senate and House of Representatives must

pass this month to avoid a Sept. 30 government shutdown.

Congressional aides, who requested anonymity to discuss

ongoing negotiations, insisted there would be a solution, given

strong bipartisan support for assisting Ukrainian President

Volodymyr Zelenskiy's government.

Zelenskiy travels to the United States this month and hopes

to present a "victory plan" to Biden. He is expected to take

part on Friday in a meeting of the Ramstein group of nations,

including the U.S., which supplies arms to Ukraine.

U.S. COMPANIES BENEFIT

Congressional aides said it was not fully clear why the flow

of weapons to Ukraine had slowed this year, but said it was

partly due to U.S. Department of Defense concern that its own

stocks were being depleted, as the weapons industry struggles

with supply chain issues.

Lawmakers who back Ukraine, from both parties, stressed the

importance of continuing the support.

"Bipartisan support for Ukraine is critical to American

interests, and we will do whatever we can in 2024 to build on

these successes and secure additional future military aid

necessary to maintain the momentum," Democratic Senator Richard

Blumenthal and Republican Senator Lindsey Graham, said in a

statement last month after their sixth visit to Ukraine.

Congress has approved nearly $175 billion of aid and

military assistance for Ukraine and allied nations since Russia

launched its full-scale invasion in February 2022.

Much of that has come in the form of long-term funding for

U.S. defense production, as the Pentagon looks to replace

equipment sent to Kyiv. Biden administration officials and

Ukraine supporters in Congress have stressed the benefits for

U.S. producers as they look to overcome the resistance from a

vocal bloc of Republicans who say taxpayer money should be spent

at home, not sent abroad.

Companies like RTX's Raytheon in Arizona which

makes Patriot missile systems and General Dynamics' ( GD ) 155

millimeter artillery plants in Pennsylvania, are receiving

contracts for products that will replace those sent to Ukraine

using PDA. Arizona and Pennsylvania are among the "swing" states

expected to decide the Nov. 5 U.S. presidential election.

As negotiations with Congress continue, the administration

is considering a backup plan, according to sources familiar with

the discussions, in which the State Department would make a

substantial PDA announcement before the Sept. 30, effectively

spending the remaining $6 billion before it expires.

Under this contingency plan, the delivery timeline for the

weapons and equipment would be extended, sources said, allowing

for a more gradual transfer of resources to Ukraine.

Congressional aides and administration officials also note

that there is another resource available: about $3 billion in

PDA authority resulting from a Pentagon accounting error remains

available to help Ukraine. It does not expire.