WASHINGTON (Reuters) -SpaceX said on Thursday it "forcefully rejects" the Federal Aviation Administration's conclusion that Elon Musk's company failed to follow U.S. regulations during two rocket launches - alleged violations that led the agency this week to propose $633,000 in fines.

The FAA on Tuesday faulted SpaceX's actions ahead of launches in June and July of 2023 in Cape Canaveral, Florida, prompting Musk to call the fines politically motivated and threaten to sue to contest them.

Musk has chafed for years at what he sees as government inefficiency and has battled with federal regulators. SpaceX must obtain FAA signoffs for rocket launches and new technology.

David Harris, SpaceX vice president for legal, sent a letter on Thursday to the leaders of two congressional committees that oversee the FAA, expanding on the company's objections and asserting its commitment to safety.

"SpaceX forcefully rejects the FAA's assertion that it violated any regulations," Harris wrote.

The FAA, Harris wrote, was failing to "keep pace with the commercial spaceflight industry" and suggested the fine may be the agency's response to increased congressional scrutiny of the FAA's oversight of the commercial space industry.

SpaceX said it has been clear for some time the FAA's commercial space office "lacks the resources to timely review licensing materials" and "mistakenly focuses its limited resources on areas unrelated to its public safety regulatory scope."

The FAA declined immediate comment.

In proposing the fines, the FAA said SpaceX failed to obtain approval to revise the communications plan related to its license for the June 2023 launch of a rocket carrying an Indonesian telecommunication satellite. The agency said SpaceX added a new launch control room without approval and removed a mandatory phone call between the company, FAA and other launch staff concerning pre-launch readiness procedures.

SpaceX said the FAA failed to review changes in a timely manner before the launch even though the agency had advance notice of six weeks, and added that the changes it made were ones that did not require regulatory approval.

The FAA also said SpaceX used an unapproved network of propellant tanks that send fuel to the rocket before the July 2023 launch of a communications satellite for the company Echostar. SpaceX said the FAA subsequently approved the use of this network of tanks for a subsequent launch and decided it would not impact safety.

SpaceX has 30 days to formally respond to the FAA.

In February 2023, the FAA proposed a $175,000 civil penalty against SpaceX for failing to submit some safety data to the agency prior to an August 2022 launch of Starlink satellites. The company paid that fine, according to the FAA.

In September 2023, the FAA completed an investigation into SpaceX's April 2023 test launch of its giant Starship rocket, requiring the company to implement dozens of corrective measures.

Republican presidential candidate Donald Trump has said he would establish a government efficiency commission headed by Musk if he wins the Nov. 5 election. Musk has endorsed Trump.