WASHINGTON — In the face of an unyielding Congress, President Obama said Monday he will no longer wait for Republicans to act on a sweeping immigration overhaul and will move on his own to make policy changes in what has been a top second-term priority of his presidency.

Obama’s decision to take a targeted approach at the immigration system signals the end of a years-long quest for legislation that also proved elusive for President George W. Bush. It also illustrates the deep-rooted and complicated politics of immigration within the Republican Party.

Obama said he will refocus immigration enforcement onto a Mexican border that has seen a tide of children crossing illegally from Central America. That means putting resources into deporting people who are the most recent border-crossers or individuals who pose a threat to public safety and national security.

He also said he has instructed Homeland Security Secretary Jeh Johnson and Attorney General Eric Holder to recommend ways to bypass Congress with executive actions that “fix as much of our immigration system as we can.” He said he expects those recommendations before the end of the summer and said he would adopt them promptly.

“I take executive action only when we have a serious problem, a serious issue, and Congress chooses to do nothing,” Obama said. “And in this situation, the failure of House Republicans to pass a darn bill is bad for our security, it’s bad for our economy and it’s bad for our future.”

Obama said he decided to act on his own after House Speaker John Boehner informed him last week that the House would not vote on an immigration overhaul this year.

Arguing there are enough Republicans and Democrats in the House to pass an immigration bill today, Obama said he had chosen to wait for more than a year to give Boehner space to act.

Obama said the thousands of unaccompanied children showing up on the border underscore the need to drop the politics and act on immigration.