US Gen.: An Iranian Nuke Would Spark Arms Race

James Mattis: still sanctions could still work, but other "means" available.

March 5, 2013 — -- A high-level U.S. military commander said today that if Iran is allowed to develop a nuclear weapon, another country in the region has already pledged to do the same.

"At least one other nation has told me they would do that," said Gen. James Mattis, the commander of the U.S. Central Command, before an open hearing for the Senate Armed Services Committee. "At a leadership level, they have assured [me] they would not stay without a nuclear weapon" if Iran had one.

Mattis said he feared that Iran obtaining a nuclear weapon would be the "most destabilizing event that we could imagine for the Middle East."

Mattis did not identify the regional actor to which he was referring, but answered in the affirmative after Sen. Lindsey Graham (R-S.C.) asked if it was a "Sunni Arab state." And Mattis said he didn't believe it would necessarily end there, saying other "non-Sunni Arab states in the general region" may seek a similar capability.

Iran, which is dominated by Shiite Muslims, is for the most part surrounded by countries in which a majority of the population is Sunni. In December 2011, a Saudi Arabian prince, Turki al-Faisal, reportedly suggested that his country, a powerful regional rival led by Sunni Arabs, would consider a nuclear weapons program should it become clear Iran had obtained the bomb. Last October, Israeli Defense Minister Ehud Barak told a British newspaper he believed Egypt and Turkey would follow suit. Israel is widely believed to already possess nuclear weapons of their own, but the government has not confirmed their existence publicly.

The "likely" possibility that an Iranian nuclear weapon would lead "other governments in the region to pursue their own nuclear weapons programs" was noted in the new Nuclear Iran Prevention Act of 2013, legislation introduced to the House last week by Rep. Ed Royce (R-Calif.) with 48 co-sponsors.

However, some analysts believe the threat of a Middle Eastern nuclear domino effect is overly hyped.

Colin Kahl, a senior fellow at the Center for New American Security, wrote in a report last month that Saudi Arabia would have "significant disincentives" to conducting a crash course on nuclear weapon development in response to an Iranian nuke, particularly if it relies on nuclear-armed Pakistan for help. Kahl told ABC News today that doing so would make both countries "extraordinarily vulnerable to international sanctions and rupture the security relationship with the United States."

Also, Kahl said he believes Saudi Arabia is at least a decade away from having the rudimentary infrastructure necessary to support such an effort, making that possibility "a long way away."

Joseph Cirincione of the anti-nuclear proliferation group Ploushares Fund also questioned whether a regional arms race might be triggered if Iran obtains a nuclear weapon and looked to North Korea as a counter-point to the U.S. and Israeli officials' warning words.

Cirincione noted that the small Asian nation has conducted three nuclear tests since 2006 and -- save for the already nuclear-armed China and Russia -- said its smaller neighbors still have not sought to match the capability. He said a nuclear Iran might set off regional discussions, but he too believes Saudi Arabia would be risking too much by attempting to join the nuclear club.

"Would Saudi Arabia really break its alliance with the United States and pull out of the Non-Proliferation Treaty?" he said.

As for Egypt and Turkey, Steven Cook at the Council on Foreign Relations wrote in a March 2012 Foreign Policy report that they too would likely not have the combination of will and ability to pursue a weaponized nuclear program even with Iranian prompting.

'We Can Bring Them To Their Knees?'

Mattis said today he believes economic sanctions still have a chance of dissuading the Iranian leadership from pursuing a bomb in the first place, should unpopularity in the streets trump nuclear ambitions.

"But if that doesn't work, we can bring them to their knees?" Sen. Graham asked, apparently referring to American military capabilities.

After a long pause, Mattis replied, "Yes sir. There are a number of means to do that, perhaps even short of open conflict. But certainly that's one of the options I have to have prepared for the President."

Mattis' comments come the same day newly minted Secretary of State John Kerry told ABC News' Martha Raddatz that Iran continues to move closer to developing a nuclear weapons capability.

"Lines have been drawn before and they've been passed," Kerry said. "That's why the president has been so definitive this time. This is a very challenging moment with great risks and stakes for everybody because the region will be far less stable and far more threatened if Iran were to have a nuclear weapon."

For years Iranian leaders have maintained the country's nuclear program is strictly for peaceful energy purposes.

ABC News' Rym Momtaz and The Associated Press contributed to this report.