WASHINGTON — President Obama will announce executive actions on Tuesday intended to expand background checks for some firearm purchases and step up federal enforcement of the nation’s gun laws, White House officials said Monday, once again trying to sidestep a gridlocked Congress on a politically divisive issue.

But faced with clear legal limitations on his authority, Mr. Obama will take modest steps that stop well short of the kind of large-scale changes to the gun trade that he unsuccessfully sought from Congress three years ago. That legislation would have closed loopholes that allow millions of guns to be sold without background checks at gun shows or in online firearm exchanges.

Instead, Mr. Obama will clarify that existing laws require anyone making a living by selling guns to register as a licensed gun dealer and conduct background checks. White House officials said the president would note that criminal penalties already exist for violating those laws.

“We have to be very clear that this is not going to solve every violent crime in this country,” Mr. Obama said on Monday, ahead of a formal announcement on Tuesday. “It’s not going to prevent every mass shooting; it’s not going to keep every gun out of the hands of a criminal.”