By Scott Malone
MANCHESTER, N.H. (Reuters) - U.S. Senator Marco Rubio, a potential candidate for the Republican presidential nomination, on Tuesday said Congress should deal with Islamic State militants by authorizing use of military force that is not limited in duration or geography but stop short of making a declaration of war.
Speaking to voters in New Hampshire, which will hold the United States' first 2016 presidential nominating primary, the Florida Republican said that placing too tight a rein on the authorization of force would be a mistake.
"So you're going to do an authorization of use of force that says we authorize you to fight them for three years, so what does that mean? That means that if ISIS is still around in three years they get to stay?" Rubio asked an audience of a few hundred people at the New Hampshire Institute of Politics in Manchester.
Limiting operations to Syria or Iraq, where the group has already seized territory, could push them elsewhere in the region, he said.
President Barack Obama this month asked Congress for authorization for limited military action against Islamic State militants, against whom the United States has been conducting air strikes in Iraq since August.
Rubio said he would stop short of declaring war on the group, which is also known as ISIS.
"We only declare war on nation-states," said Rubio, who was elected in 2010 on a wave of support from the conservative Tea Party movement. "ISIS wants to be considered a state but it is not a state and I refuse to elevate it to that standing."
Recent polls have Rubio running in the bottom half of the crowded Republican field. An NBC News/Marist poll released earlier this month showed him with the support of 6 percent of potential primary voters, one-third the support of fellow Florida Republican and front-runner Jeb Bush.
Rubio received a warm reception, although most said they were far from deciding which candidate they would support.
"He's optimistic and that's what the country needs right now," said Donna Sytek, the former speaker of the state house, who compared Rubio to former President Ronald Reagan.
Others suggested that Rubio's relative youth - he is 43 years old - would limit his prospects in 2016.
"The challenge for him is that this isn't a party that goes with young, up-and-coming leaders," said Peter Ubertaccio, a professor of political science at Stonehill College in neighboring Massachusetts. "I think it's going to be an uphill battle."
(Reporting by Scott Malone; Editing by Bill Trott)