LAS VEGAS (AP) President Barack Obama says “now is the time” to fix broken immigration laws. And he says Congress is showing “a genuine desire to get this done soon.”

At a campaign-style event in Las Vegas, the president applauded a rare show of bipartisanship between the White House and Senate lawmakers on basic plans for putting millions of illegal immigrants on a pathway to citizenship and tightening security at the borders.

But mindful of previous immigrations efforts that have failed, Obama warned that the debate would become more difficult as it gets closer to a conclusion.

Both the White House and Senate proposals still lack key details. And potential roadblocks are already emerging, even before a Senate measure can be debated, approved and sent to the Republican-controlled House where opposition is likely to be stronger.