President Trump on Monday promised “no change” to workers’ 401(k) retirement plans — just days after reports that Republicans were weighing a move to slash the annual cap on annual contributions.

“There will be NO change to your 401(k),” Trump tweeted. “This has always been a great and popular middle class tax break that works, and it stays!”

Congressional Republicans, as part of a plan to offset an expected drop in tax revenue from the White House’s ambitious tax overhaul framework, reportedly had been discussing lowering the cap on tax-deferred payments to $2,400 from the current $18,000 level for most workers.

By lowering that cap, Uncle Sam’s tax revenues would increase because less employee income would be shielded with the 401(k) provision.

If enacted, US workers would have to switch to Roth IRAs, which are taxed on the front end but are shielded from taxes on the back end when the money is withdrawn.

The IRS was also expected to raise contribution limits next year to $18,500.

The Fidelity Group, the second-largest money manager in the world with $4.5 trillion, told The Post on Friday that the proposal under consideration by Republicans “greatly concerned” them.