A senior White House national security official said the president is comfortable with the disagreement and "wants to see the kind of creative tension and full-out debate that major policy decisions engender."

The official added, "It's the president's view that ... frankly, that kind of debate among two Cabinet officers like Secretary Gates and Secretary Napolitano, both of whom he holds in high regard, will inevitably lead to a better policy."

The official noted that the administration has already taken some steps, sending 450 DHS and Justice Department agents to the border in March to fight cash and weapons smuggling. And, he pointed out, crime in U.S. border communities and border arrests have fallen.

For now, administration officials are working through differences. In response to the Pentagon concerns that the troops could become permanent, DHS officials are searching for benchmarks that would end a deployment, such as a drop in cartel violence or improved Mexican enforcement.

When the Bush administration sent Guard units to the border, they went as a stopgap measure, backing up the U.S. Border Patrol for two years while it added 6,000 agents. The troops rotated through non-law enforcement duties.