The top Republican on the Senate Foreign Relations Committee says that, under the Constitution, President Obama must seek congressional approval to attack Libya, something Defense Secretary Robert Gates said would be the first step of instituting a no-fly zone the United Nations just approved.

Now, Sen. Richard Lugar, Indiana Republican, is heading to the White House for a meeting about the issue at 12:30, according to Lugar spokesman Mark Helmke.

The meeting comes one day after Lugar insisted congressional authorization is needed for any attack on Libya at a committee hearing.

“If we are going to declare war against Libya, we ought to have a congressional declaration of war,” Lugar said.

President Obama, Vice President Biden and Secretary of State Hillary Clinton all insisted as candidates for the Democratic presidential nomination that presidents need congressional authorization to attack foreign countries in all but emergency situations.

“The President does not have power under the Constitution to unilaterally authorize a military attack in a situation that does not involve stopping an actual or imminent threat to the nation,” Obama said as a candidate and then-senator.