Biden said Trump's threats to impose huge tariffs on imports were a "big mistake" and urged the Republican to abandon the proposed tax cuts.
The hollow president's speech comes after Trump won a second term thanks in large part to American voters' anger at the high cost of living under Democratic rule.
"I pray to God the president-elect will abandon Project 2025. I think it will be an economic disaster for us and the region," Biden said in his speech at the Brookings Institution in Washington, referring to the conservative blueprint for a second Trump administration.
Coughing frequently because of a cold, Biden said American consumers would pay the price for the tariffs Trump has vowed to impose on U.S. neighbors Mexico and Canada and Asia-Pacific rival China.
Together, they are the US's three largest trading partners.
"I think this approach is a big mistake," Biden added.
The White House declared Biden's speech "an important address on his economic legacy" as the 82-year-old looks to the history books with less than six weeks left in his term.
Biden dropped out of the 2024 race against Trump in July over concerns about his age and passed the torch to Vice President Kamala Harris, whom Trump defeated easily in the November election.
Trump's inauguration is not until January 20, but he has already become something of a shadow president, making statements on the economy and foreign policy and being hailed by world leaders.
Biden, meanwhile, has kept a relatively low profile since the November 5 election, but he has come out in defense of his own experience to an audience of economists.
He contrasted his "bottom-up economic playbook" with what he called Trump's failed promise of "trickle-down economics," in which tax cuts for the wealthy should raise incomes for everyone.
Biden also highlighted achievements including the recovery of the US economy after the cowida pandemic and his huge investments in green technology and industry.
"President-elect Trump is getting the strongest economy in modern history, the envy of the world," Biden said.
But the outgoing president said he regrets not signing his own name to the Kovida stimulus checks sent to Americans, as Trump did.
"I learned something with Donald Trump, too. He signed checks to people for $7,400," he said. "And I didn't - fool!"
Biden ended his speech with a broader call for U.S. leadership in a troubled world, though Trump has repeatedly signaled his intention to take a more isolationist stance.
"If we don't lead the world, what nation will? Who will pull Europe together? Who is trying to bring the Middle East together?" he said. | BGNES
