* Napolitano to push legislation in Congress

* McCain says reform must include temporary worker program

* Failure to pass may delay issue for generation -senators

By Doug Palmer

WASHINGTON, June 25 (Reuters) - President Barack Obama tapped a top Cabinet official on Thursday to work with Congress to speed immigration reform as senators warned another failed effort could doom chances for a generation.

"Despite our inability to get this passed over the last several years, the American people still want to see a solution," Obama told reporters after meeting with Democratic and Republican lawmakers.

Obama said he had asked Homeland Security Secretary Janet Napolitano to meet regularly with lawmakers to systematically work through a number of controversial issues, such as how to handle the 12 million illegal immigrants already in the United States and how to prevent future illegal immigration.

"It's going to require some heavy lifting. It's going to require a victory of practicality and common sense and good policymaking over short-term politics," Obama said.

Congress failed in 2006 and 2007 to pass immigration reform despite a push by former Republican President George W. Bush.