LAS VEGAS (AP) — Mounting an offensive behind his immigration directives, President Barack Obama on Friday insisted House Republicans must take up a comprehensive immigration overhaul but said the system is so unfair that it needs the type of fixes that he initiated on his own.

"Our immigration system has been broken for a very long time and everybody knows it," he said. "We can't afford it anymore."

Speaking at the Las Vegas high school where he launched his drive for Congress to send him an immigration bill, Obama outlined steps he has taken to help millions of people living in the country illegal. The measures are designed to make nearly 5 million of those immigrants eligible for protection from deportation and for work permits.

But he cautioned that his actions are limited and that only broader legislation would permanently change immigration laws and help the more than 11 million immigrants illegally in the United States.

"The actions I've taken are only a temporary first step," he said.

As if to underscore that point, a heckler interrupted Obama, chiding him for not doing enough with his executive actions to help more immigrants in the country.

"Not everyone will qualify," Obama conceded. "That's the truth. Listen, I heard you and what I'm saying is we're still going to have to pass a bill."

With Republicans accusing him of overstepping his authority, Obama and his allies are seeking to sell the executive actions on immigration as good politics and good policy.

The effort is crucial to Obama as he tries to dampen Republican cries to undo the administrative measures and, at the same time, strives to win the trust of immigrants and get them to participate.

The executive actions, which Obama laid out in a prime-time television address Thursday, would mainly cover parents of U.S. citizens and of legal residents as long as the parents have been in the U.S. for five years or more. But Obama's actions also would change enforcement priorities by emphasizing the deportation of new illegal arrivals and criminals.

House Speaker John Boehner, R-Ohio, said Obama, in sidestepping Congress, had damaged his ability to get things done.

"By ignoring the will of the American people, President Obama has cemented his legacy of lawlessness and squandered what little credibility he had left," Boehner said in a statement following Obama's speech.

But Obama countered that it has been Republicans who have stood in the way, noting that 512 days have passed since the Senate passed a comprehensive bill.

"The only thing that's been standing in the way, is a simple yes or no vote in the House of Representatives. Just a yes or no vote," he said. "If they had allowed a vote on that kind of bill, it would have passed. I would have signed it. It would be the law right now."