Syrian President Bashar al-Assad gives a press conference after his meeting with his Austrian counterpart Heinz Fischer on April 27, 2009 in Vienna at the start of his two-day state visit. (DIETER NAGL/AFP/Getty Images)

Last month’s alleged chemical attack near Damascus has re­focused attention on Syria’s 30-year-old biological weapons research and raised concerns about whether the government there could activate an effort to make a weapon.

Syria’s bioweapons program, which U.S. officials believe has been largely dormant since the 1980s, is likely to possess the key ingredients for a weapon, including a collection of lethal bacteria and viruses as well as the modern equipment needed to covert them into deadly powders and aerosols, according to U.S. and Middle Eastern officials and weapons experts.

This latent capability has begun to worry some of Syria’s neighbors, especially after allegations that the regime of President Bashar al-Assad used internationally banned chemical weapons against civilians in an Aug. 21 attack.

Top intelligence officials in two Middle East countries said they have examined the potential for bioweapons use by Syria, perhaps as retaliation for Western military strikes on Damascus. Although dwarfed by the country’s larger and better-known chemical weapons program, Syria’s bioweapons capability could offer the Assad regime a way to retaliate because the weapons are designed to spread easily and leave few clues about their origins, the officials said.

“We are worried about sarin, but Syria also has biological weapons, and compared to those, sarin is nothing,” said a senior Middle Eastern official, who like several others interviewed for this report agreed to discuss intelligence assessments on the condition that his name and nationality not be revealed. “We know it, and others in the region know it. The Americans certainly know it.”

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U.S. officials acknowledge the possibility of a latent bioweapons capability but are divided about whether Syria is capable of a sophisticated attack.

Historically, at least a half-dozen countries have manufactured biological weapons, including the United States, Britain and Russia, all of which abandoned their programs. Syria is one of the few countries that Western intelligence agencies suspect continued some research.

Syria appeared to publicly acknowledge its biological weapons capability in an unusual statement in July 2012 by the country’s Foreign Ministry spokesman, Jihad Makdissi. Responding to Western reports about Syria’s chemical weapons stocks, Makdissi said in a televised interview that the regime would never use “any chemical and biological weapons” inside Syria. He said the Syrian military was safeguarding “all stocks of these weapons.”

It was the first direct acknowledgment by Syria that such stockpiles might exist, and Makdissi’s voluntary mention of biological weapons took many analysts by surprise. Shortly afterward, the spokesman retracted his remarks in a statement posted on Twitter, saying Syria had no chemical or biological weapons of any kind.

But other governments, including the United States, have long believed that Syria had developed at least a rudimentary biological weapons capability along with its massive stockpile of chemical munitions.

A report prepared for Congress this year by the Office of the Director of National Intelligence concluded that Syria possesses a “longstanding biological weapons program,” adding that parts of it “may have advanced beyond the research and development stage, and may be capable of limited agent production.”

Other intelligence assessments have been more cautious, citing a lack of hard evidence that Syria’s fledgling efforts progressed to “weaponizing” pathogens for use in military rockets and shells. But some officials and independent experts say military biological weapons are not needed to launch a bioterrorist attack on civilians.

“We know that they went at least as far as research and development,” Rep. Mike Rogers (R-Mich.), chairman of the House Permanent Select Committee on Intelligence, said in an interview. “That means they’re far enough along to have capabilities. It doesn’t take a huge leap to get from there to having the ability to weaponize or finding some other way to deliver.”

Syria’s early research on cultivating strains into weapons has been confirmed by multiple Western governments, with U.S. intelligence agencies tracking the country’s efforts through the 1970s and 1980s to counter arch-rival Israel’s nuclear weapons and conventional military dominance. In 2001, a declassified CIA assessment asserted that it was “highly probable” that Syria was developing an “offensive BW capability.” U.S. assessments have frequently cited the Scientific Studies and Research Center in Damascus, a military-run laboratory previously linked to covert programs for research on chemical and nuclear weapons.

A 2008 profile of Syria’s unconventional weapons programs by the Washington-based Center for Strategic and International Studies concluded that its military had developed “probable production capacity for anthrax and botulism, and possible other agents.” The report said delivery systems for such weapons were within the grasp of Syria’s armed forces, which have long possessed missiles and rockets tipped with warheads.

“So is the use of proxy or covert delivery,” stated the report, written by Anthony Cordesman, one of the center’s strategic analysts.

Although little is publicly known about the state of Syria’s bioweapons program today — including whether it is active — the country has gained new capabilities in recent years through massive government investments in its pharmaceutical industry. Much of the equipment acquired by Syria’s military laboratories in recent years is regarded as “dual-use” and can be used either for weapons or legitimate research, said Jill Bellamy van Aalst, a scientist and a biodefense consultant to NATO and the European Union.

Van Aalst, who has studied Syria’s weapons facilities for a decade as part of her research for a book, says the country’s bioweapons program, whatever its size, is capable of serious harm. Many of the basic elements have been in place for years, she said, including what she described as a full complement of lethal human and animal strains, from neurotoxin producers such as botulinum to the family of orthopox viruses such as camelpox and cowpox, both cousins to the microbe that causes smallpox.

“You don’t stockpile biological weapons anymore, because today it’s all about production capacity — and in Syria the production capacity is quite substantial,” van Aalst said. “The dual-use nature makes it very cost-effective. In down times, you can use the equipment for public health purposes, knowing you can ramp it up at any time. These are very agile programs.”

Other weapons experts view Syria’s biomedical expansion as intriguing but not necessarily alarming. “Syria has a chemical weapons program, so anything they do is suspect,” said Jeffrey Lewis, a weapons expert at the James Martin Center for Nonproliferation Studies in Monterey, Calif. “It’s easy to see the devil behind every woodpile. But I suspect there’s probably not a lot there.”