WASHINGTON (Reuters) - Amtrak CEO Stephen Gardner said Wednesday he will step down immediately after more than four years as head of the U.S. passenger railroad, citing concerns about maintaining the carrier's support from President Donald Trump's administration.

"I am stepping down as CEO to ensure that Amtrak continues to enjoy the full faith and confidence of this administration," Gardner said in a statement.

Billionaire Elon Musk, who is advising Trump on plans to radically shrink the U.S. government, said earlier this month he thought Amtrak should be privatized.

The White House and Transportation Department did not immediately comment on whether the administration had asked Gardner to step down. Amtrak did not respond to a request for comment.

Trump during his first term repeatedly sought to cut funding to Amtrak, which received about $2.4 billion in annual federal support in 2023. Congress last week approved $2.42 billion for Amtrak through September 30 in annual funding.

Amtrak said in December ridership topped 2019 pre-COVID-19 levels for the first time in 2024 and reached a record high even with less capacity. Ridership increased over 15% in 2023 to a record 32.8 million customer trips, as passenger revenue hit $2.5 billion, up 9% over the prior year. The rail operator reported an adjusted operating loss of $705 million for the 12 months ended September 30, down 9% versus 2023.

Amtrak in March said it was boosting passenger services on the East Coast as it aims to double ridership nationwide by 2040 to 66 million passengers.

Congress approved $66 billion for rail projects as part of a massive infrastructure bill in 2021, with $22 billion dedicated to Amtrak over five years on top of regular funding.

In 2023, then President Joe Biden announced $16.4 billion in grant funding for 25 rail projects on Amtrak's Northeast Corridor -- Boston to Washington -- which is the busiest U.S. rail corridor with 800,000 daily trips in a region representing 20% of the U.S. economy.

Many bridges, tunnels and other parts of the corridor are in serious need of repairs, especially a key tunnel connected New York City and New Jersey.