WASHINGTON (AP) -- The U.S. and its allies are closely monitoring Syria's large stockpiles of chemical arms and portable anti-aircraft missiles, a State Department official said Wednesday, amid concerns that the country's unconventional weapons could fall into the hands of terrorist or militant groups while the 11-month-old uprising continues.
Thomas A. Countryman, assistant secretary of state for international security and nonproliferation, drew a parallel with allied efforts to secure loose weapons in Libya during the fighting there, but called the situation in Syria "much more difficult."
"When you get to a change of regime in Syria -- and of course we don't know when that is -- it matters a great deal what are the conditions, whether it is a chaotic or a fairly orderly transfer " of power, Countryman told reporters. "We would certainly be prepared to work with any successor government to help them secure control of those weapons with the goal of destroying them."
Officials have said that the U.S. in particular is talking with its allies on ways to ensure that Syria's stockpile of portable anti-aircraft missiles, called Man-Portable Air Defense Systems, or MANPADS, aren't stolen or diverted.
"At this point we do wish to have the neighbors of Syria do something of the same prudential planning that the neighbors of Libya are doing," Countryman said, to try to stop weapons trafficking across their borders.
Countryman estimated that Syria has "tens of thousands" of the portable missiles, which are considered a threat to commercial aviation. The U.S. estimates that Libyan leader Moammar Gadhafi had amassed an arsenal of 20,000 of the weapons.
Matthew Schroeder, a small arms researcher with the Federation of American Scientists, noted that Countryman's figure was much larger than previously published estimates, which put the number of Syria's portable missiles at just over 4,000. "Are Syria's stockpiles more advanced than Libya's? If so, this could be even more dangerous," Schroeder said.
Republicans in Congress have been critical of U.S. efforts to secure Libya's chemical and unconventional arsenals, saying the Obama administration should have responded more quickly during that crisis and now faces the task of trying to account for thousands of missing weapons.
"We got off to a slow start with Libya," Rep. Edward Royce, R-Calif., chairman of the House Foreign Affairs subcommittee on terrorism, nonproliferation and trade, said in an interview.
The U.S. had a much better picture of Libya's weapons stockpile than it has of Syria's. Tripoli halted its weapons of mass destruction programs in 2003 as part of an agreement reached to improve relations with the West, and Moammar Gadhafi's remaining stocks of mustard gas were awaiting destruction when rebels drove him from power last year.
Syrian President Bashar Assad is believed to have nerve agents as well as mustard gas, Scud missiles capable of delivering these lethal chemicals and a variety of advanced conventional arms coveted by insurgent and terrorist groups, including late-model MANPADS and anti-tank rockets.
U.S. intelligence officials in the past have said Syria has conducted biological weapons-related research but have stopped short of saying the country had taken the next step and built bioweapons.
Israel and its allies long have suspected Syria of seeking at least the capacity to build atomic weapons, and the U.N. nuclear watchdog agency has pressed for information about its nuclear research program. But a 2007 Israeli airstrike on a suspected plutonium-producing reactor under construction in northern Syria may have derailed Syria's nuclear ambitions.
Israeli officials this month said their main worry is that Syria's ally, the militant group Hezbollah, could acquire Syria's Soviet-design S-125 surface-to-air missile systems, which could hinder operations by the Israeli air force. But Israeli officials also said they were concerned Hezbollah could get its hands on chemical weapons and missiles capable of striking deep inside Israel.
Syria's chemical arms are believed to be secure for now because they are stored at weapons depots in rural areas, officials and experts say, away from the urban centers where most fighting is now taking place.
"So far at least I don't think we've seen any examples among troops that are guarding these sites or any activities to suggest the chain of command is weakening," said Leonard Spector, a former senior nonproliferation official with the National Nuclear Security Administration. "I think what people are worried about is that the situation could become increasingly chaotic and the chain of command breaks down."
But if Syria's control of its arsenal collapses, he said, the consequences could be worse than in Libya. "It's a hundred times more serious in Syria," he said.
Andrew Shapiro, the assistant secretary of state for political-military affairs, said this month that the U.S. has helped recover 5,000 of Libya's portable anti-aircraft missiles, or about a quarter of the total.
Shapiro said many of the weapons that have not been accounted for were likely used in training, had broken down or were fired by rebels while fighting the regime. A substantial number probably remain in the hands of militias who defeated Libyan government forces and were often the first to "liberate" weapons sites, he said.
"Yet clearly we cannot rule out that some weapons may have leaked out of Libya," Shapiro told a non-proliferation group.
The U.S. plans to spend $40 million helping Libya secure and recover its stockpiles of portable anti-aircraft weapons, Shapiro said. The U.S. also will conduct an inventory of all Libyan weapons storage areas and has two mobile teams assigned to respond to the discovery of new portable missile caches, he added.
Royce and other Republican lawmakers said that if Syria's arsenals are threatened, the Obama administration should move faster than it did in Libya to secure unconventional weapons.
AP National Security Writer Robert Burns contributed to this report.