The Wall Street Journal reports:

The U.S. and Israel are closely monitoring Syria’s suspected cache of weapons of mass destruction, fearing that terror groups could take advantage of the revolt against President Bashar al-Assad to obtain blistering agents, nerve gas and long-range missiles, according to officials from both countries.

U.S intelligence services believe Syria’s nonconventional weapons programs include significant stockpiles of mustard gas, VX and Sarin gas and the missile and artillery systems to deliver them.

United Nations investigators also recently concluded that Damascus had been secretly constructing a nuclear reactor with North Korean help before Israeli jets destroyed the site in late 2007. U.S. and U.N. nonproliferation officials continue to worry that Pyongyang may have provided Syria with additional nuclear-related equipment.

“We are very concerned about the status of Syria’s WMD, including chemical weapons,” Israel’s ambassador to the U.S., Michael Oren, said in an interview. “Together with the U.S. administration, we are watching this situation very carefully.”

Israel has historically held concerns about the fall of the Assad regime, which has largely kept the Syria-Israel border quiet for the past 40 years. Still, Prime Minister Benjamin Netanyahu’s government has increasingly voiced support for democratic change in Damascus.

“We see a lot of opportunity emerging from the end of the Assad regime,” Mr. Oren said.

A senior U.S. official said Syria’s suspected chemical weapons arsenal “is of great importance and…under intense study.”

U.S. and Israeli officials won’t disclose exactly how they are keeping tabs on Syrian weaponry. But in the past, the U.S. and Israel have tracked activities at Syrian military installations using satellites and human spies. In 2008, the George W. Bush administration released detailed photographs and other intelligence of a reactor allegedly set to produce weapons-grade plutonium on the Euphrates River in eastern Syria.

Washington’s concerns about Syria mirror in some ways those held about Libya, where U.S. intelligence agencies are trying to help rebels secure mustard gas, shoulder-fired missiles and light arms amassed by Col. Moammar Gadhafi’s regime in recent decades. The Obama administration is concerned these weapons could fall into the hands of militant groups and terrorist organizations operating across North Africa and the Middle East.