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Prodding Republicans to get onboard, President Obama on Thursday called on Congress to tackle a comprehensive immigration overhaul and warned that a failure to do so could trigger a harmful "patchwork" of local laws similar to the one recently passed in Arizona.

While Arizona lawmakers defend their law as necessary to patrol the border, Obama described it as "unenforceable" and a vehicle for civil rights abuse. He said a "national standard" is needed and that he won't "kick the can down the road" any longer.

"I'm ready to move forward, the majority of Democrats are ready to move forward, and I believe the majority of Americans are ready to move forward," Obama said.

The president blamed Republicans for exacerbating the problem. He suggested places like Arizona are unilaterally taking up the issue because GOP senators backed away from immigration reform following the debate several years ago led by Sen. John McCain, R-Ariz., and the late Sen. Ted Kennedy, D-Mass. Obama blamed political posturing and "demagoguery" for Washington's inability to deal with the problem, pressing Republicans to step up.

"The fact is without bipartisan support, as we had just a few years ago, we cannot solve this problem," Obama said at American University in Washington, D.C.

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One of those senators, Sen. Jon Kyl, R-Ariz., told Fox News he wasn't basing his resistance on "demagoguery." He said he's pressing for better border security first because that's what his constituents want.

"It was very political," Kyl said of the speech.

But Obama cast his legislative pitch as an attempt to find middle ground between the two "poles" of the debate. He criticized the idea of granting "blanket amnesty" as well as the idea of deporting all illegal immigrants. Rather, he called for a "pathway to legal status" that would have illegal immigrants get in line and pay a fine.

"The overwhelming majority of these men and women are simply seeking a better life for themselves and their children," he said.

Obama called for reforms to the legal immigration system and defended the attempts his administration has made so far to improve border security -- though Kyl said it's not enough.

Amid cries for tougher enforcement on one side and leniency on the other, Obama said he hears the "frustration" Americans have expressed about a "system that seems fundamentally broken."

He said that system would be "no exception" to the national challenges he's committed to tackling.

The call to action is a heavy lift for the president, who is keeping Congress' plate overflowing. As he tries pulling a financial regulation package over the finish line and begins implementing provisions of the health care bill, he's also pushing anew for action on a climate package. The speech on immigration follows back-to-back meetings Obama had with advocates and lawmakers at the White House this week.

The controversial Arizona immigration law may have served as the impetus for a stepped-up federal push -- but it also highlighted how critical border-state lawmakers view the enforcement end of the debate.

Republicans have cautioned the president not to push ahead with a comprehensive immigration package until he does more to physically secure the border. And as Obama said, the political reality is that to get a bill he needs Republican support, mostly in the Senate, where Democrats fall short of the 60 votes needed to overcome GOP stalling tactics.

Obama has endorsed a proposal by Sens. Chuck Schumer, D-N.Y., and Lindsey Graham, R-S.C., that would require illegal immigrants, among other things, to admit they broke the law, pay fines and back taxes and perform community service to eventually obtain legal status. But Graham since has balked at acting on immigration this year, and no other Senate Republican has come forward.

Obama's administration has acted to improve border security, including increasing personnel and equipment along the border. Obama recently ordered 1,200 National Guard troops to the border to boost security and asked Congress for an additional $600 million to support personnel and improve technology there. More than 500 of those troops are to be sent to Arizona.

The Arizona law requires police enforcing another statute to clarify a person's immigration status if there's reason to believe the individual is in the U.S. illegally. Several states and communities are considering similar legislation, which Obama says is an understandable byproduct of the public's frustration over the federal government's inability to tighten the immigration system.

But Obama also has criticized the law as "misguided" and said it is potentially discriminatory. He has asked the Justice Department to review its legality and immigrant advocates are hoping the government will sue Arizona to block the law from taking effect later this month.

The Associated Press contributed to this report.