Former New York mayor and billionaire Michael Bloomberg said on Sunday he will write a $4.5 million check to cover this year's US financial commitment to the Paris Climate Agreement.
President Donald Trump last year pulled the United States out of the pact, making the country the only one opposed to it.
Bloomberg, in a CBS interview, said he hopes by next year Trump will have changed his mind.
Bloomberg will continue to provide money for the pact if the United States does not rejoin the agreement, according to a news release from Bloomberg Philanthropies, the charity he founded.
"Our foundation will uphold our promise to cover any cuts to UN climate funding by the federal government," Bloomberg said in the statement.
Trump staunchly opposes the agreement and his administration has rolled back a number of environmental regulations.