Two conservative freshmen Republican senators, Rand Paul and Marco Rubio, are sponsoring two contrasting amendments regarding the conflict in Libya – underscoring continuing disagreement among lawmakers on the issue nearly two weeks after President Obama’s authorization of U.S. military action in the country.

Paul (Ky.) on Wednesday introduced an amendment to a small business bill that would express the “sense of the Senate” that the president cannot unilaterally act on matters of war.

“The language of my resolution is not unfamiliar to many: the language of this resolution are the president’s words,” Paul said Wednesday in remarks on the Senate floor.

The symbolic resolution contains only one sentence – a statement that then-Sen. Barack Obama made in 2007 – that “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.’”

“This was very, very clear what the president said, and I agree with what candidate Barack Obama said: we should not go to war without congressional authority,” Paul said Wednesday. He added that if the country were in imminent danger, Congress would allow the president some latitude, but in this case, “even the secretary of defense has said that Libya is not in our national interest.”

“There is no threat to our national security, and yet we are involved in a third war,” Paul said.

Rubio (Fla.), sent a letter to Senate leadership on Wednesday requesting a bipartisan resolution authorizing U.S. military action in Libya and the ouster of Libyan leader Moammar Gaddafi. Rubio also asked that the resolution urge Obama to recognize Libya’s Interim Transitional National Council as the country’s governing authority.

“At the end of the day, the fact remains that our nation is not like other countries,” Rubio wrote in the letter to Senate Majority Leader Harry Reid (D-Nev.) and Minority Leader Mitch McConnell (R-Ky.). “The United States is an exceptional country with exceptional powers. But that power comes with unique moral obligations and responsibilities. The world is a better place when America is willing to lead. And American leadership is required now more than ever.”

(One interesting point about the letter is that it marks yet another instance of Rubio employing his campaign-trail “American exceptionalism” argument – only this time in favor of U.S. military intervention abroad.)

Rubio’s and Paul’s resolutions aren’t necessarily at odds with each other, but they underscore the broader divergence among lawmakers on Libya: Paul’s primary concern is congressional authority on matters of war, while Rubio’s is swift U.S. action to oust Gaddafi.

Also worth noting is the fact that the Senate has already passed a Libya resolution: earlier this month, it approved by unanimous consent a resolution sponsored by Sen. Bob Menendez (D-N.J.) calling for Gaddafi’s resignation and the possible establishment of a no-fly zone.

In other congressional responses to Libya, Rep. Dennis Kucinich (D-Ohio) is expected to take to the House floor at 12:15 p.m. Thursday to “provide an hour-long analysis of the Libyan War.”

And a group of five liberal Democrats sent a letter to House Speaker John Boehner (R-Ohio) on Wednesday calling for a “robust floor debate and vote on the president’s authority to continue use of military force in Libya.”

“It is our position that the President has a constitutional obligation to seek specific, statutory authorization for offensive military action, as he should have done with regard to U.S. military engagement in Libya,” wrote Democratic Reps. Barbara Lee (Calif.), Lynn Woolsey (Calif.), Mike Honda (Calif.), Raul Grijalva (Ariz.) and Maxine Waters (Calif.). “We look forward to working with you to address this matter on the House floor as soon as possible.”