Defense Secretary Lloyd Austin sent a weekend letter to Congressional appropriators urging them to pass government funding bills after the election in the "vulnerable time around transitions" to "uphold the bipartisan tradition of funding our nation’s defense prior to the inauguration of a new president,” a source in the department told ABC News.

In his letter to bipartisan committee chairs on government funding, Austin urged lawmakers to avoid a six-month stopgap funding measure, calling a regular funding bill for the Pentagon "the single most important thing that Congress can do to ensure U.S. national security."

Speaker Mike Johnson has proposed the six-month continuing resolution to fund the government beyond the inauguration of a new president. The government funding deadline is September 30.

Austin's letter does not signal opposition to a one-month stopgap – but he urges "action immediately after the election."

"The repercussions of Congress failing to pass regular appropriations legislation for the first half of FY 2025 would be devastating to our readiness and ability to execute the National Defense Strategy," Austin writes.

The defense secretary points out to Congressional leaders that a six-month continuing resolution "would represent the second year in a row, and the seventh time in the past 15 years" the Pentagon has been stalled until midyear in receiving its funding orders from the legislative branch.

"I am fully aware of the political pressures that will challenge the Congress from fulfilling its duty before our national elections conclude," he writes. "No matter who wins this election, there will be a Presidential transition. I urge you and your colleagues to take up action immediately after the election to limit damage to our national security during this vulnerable period around transitions and uphold the bipartisan tradition of funding our nation’s defense prior to the inauguration of a new President."