One of Donald Trump’s most vocal supporters on the City Council has sent the president a letter pleading for $3.9 billion for the MTA “to bridge the acute fiscal hemorrhaging” caused by COVID-19.

Staten Island Republican Joseph Borelli, Trump’s New York state campaign co-chair, wrote the letter sent Saturday.

It is signed by 31 fellow Council members, including Speaker Corey Johnson.

“We appreciate the $3.8 billion in federal aid to the MTA that was included in the CARES Act,” the letter said, referring to the congressional stimulus package.

But “a clearer picture of the fiscal impact has emerged,” and new data project 2020 losses from the pandemic at $7 billion to $8.5 billion.

The extra $3.9 billion “will bring some immediate relief,” but still may not be enough to make ends meet, Borelli added.

MTA Chairman Patrick Foye has reported ridership has declined 93 percent on subways, 95 percent on Metro-North, and 97 percent on the Long Island Rail Road. Tolls at bridges and tunnels are down 62 percent.

“As a New Yorker, we know that you understand the importance of the public transit system. If New York’s transit system is not able to function properly, it will have catastrophic effects on our city,” Borelli wrote.

The MTA runs the largest transportation system in North America, by far.

“If the MTA defaults on its bond obligations, it would collapse the municipal bond market and prevent the MTA from borrowing at a reasonable rate to keep the system operating,” Borelli told The Post.

Moody’s, S&P and Fitch have already downgraded the MTA’s bond ratings over the last 45 days.

MTA spokesman Shams Tarek thanked the Council members for their support.

“This letter recognizes the critical role that the MTA plays in the success of the New York metropolitan region and the entire nation’s economy,” Tarek said.