In the wake of the Newtown, Conn., school shootings in December, the group Mayors Against Illegal Guns had 100 new mayors join.

There are 800 mayors who have signed the group’s statement of principles, which include keeping “military-style weapons off our streets.” Most of the nation’s big-city mayors support the group, co-founded by New York City Mayor Michael Bloomberg.

But Charlotte Mayor Anthony Foxx – who has been outspoken in his support for a ban on assault weapons and high-magazine clips – has declined to join.

He said he has a “lot of alignment” with Bloomberg’s group but “is trying to be prudent about how I manage this issue.”

He said there are typically two groups in the gun control debate. He said there are those who want more gun control and who want to implement laws now “while the iron is hot.” On the other side, “You have a group that says under no circumstances should we change anything ... to our gun laws.”

“I think most people are somewhere in the middle,” Foxx said. “And right, wrong or indifferent, one of the concerns I have about joining any group is putting myself in a position where I can’t speak credibly to both sides.”

Foxx, a Democrat, hasn’t been silent during the gun debate.

He has said he has met twice recently with Vice President Joe Biden, who is leading a task force on curbing gun violence. Foxx on Monday signed “an open letter to the President of the United States and the Congress from the nation’s mayors.”

The letter called for enacting a ban on assault weapons and high-capacity magazines; strengthening the national background check system and eliminating loopholes; and strengthening penalties for “straw” purchases of guns.

In interviews with local media, he has called for a ban on assault weapons and said the nation’s mental health system needs improvement.

During Monday’s City Council meeting, Foxx asked city staff to track how and with whom the city spends its money for police weapons and ammunition.

Foxx easily won re-election in 2011, garnering almost 70 percent of the vote. It’s unlikely that joining Bloomberg’s group would damage him in future runs for mayor. Foxx has said he will make a formal decision about running for a third term early this year, but that he is leaning toward running again.

But Foxx has considered running for higher office. When former Gov. Bev Perdue announced last year that she wasn’t running for re-election, Foxx briefly considered running for the Democratic nomination. He decided against it, in part due to the challenges of hosting the Democratic National Convention in September.

Michael Bitzer, professor of politics and history at Catawba College, said joining a gun-control group founded by Bloomberg and Boston Mayor Thomas Menino would “raise eyebrows” in some parts of the state.

“You still have to win some rural and more importantly suburban votes,” Bitzer said about any statewide election. “It’s hard for a more liberal Democrat in this state to win statewide than a moderate slightly conservative. That stigma is something that they will have to consider in joining any association.”

Of the nation’s 50 largest cities, 32 have mayors who have joined the group. Charlotte is the nation’s 17th-largest city.

Of the 18 cities with mayors who haven’t joined, five are in Texas – a state where gun ownership is high. San Antonio Mayor Julian Castro, who was the keynote speaker at the Democratic National Convention in Charlotte, isn’t listed on the group’s website.

In North Carolina, the mayors of Raleigh, Durham, Winston-Salem and Chapel Hill have joined. Mayors in Greensboro, Wilmington, Asheville and Charlotte have not.

Some states that are considered conservative have few or no mayors who are members. Oklahoma has no mayors who have joined. Utah and North Dakota have only one mayor each.

The group was founded in 2006 by Bloomberg and Menino.

Mayors who join are asked to sign a “statement of principles.”

Some of the principles include: to “punish – to the maximum extent of the law – criminals who possess, use, and traffic in illegal guns;” to “target ... irresponsible gun dealers who break the law by knowingly selling guns to straw purchasers;” to “keep lethal, military-style weapons and high-capacity ammunition magazines off our streets;” and to “develop new technologies that aid in the detection and tracing of illegal guns.”