The newspaper said four senior U.S. officials referred to "increasing suspicions" within the intelligence community Syrian forces used chemical agents. The Journal said the suspicions were based on witness accounts and initial testing of samples recently taken from Syria and analyzed in Britain.
But other unnamed officials told the newspaper the U.S. intelligence community hasn't reached a consensus and fears the samples may have been tainted by rebels trying to draw the United States and its allies into the civil war.
If the suspicions prove true they could increase pressure on U.S. President Barack Obama to take stronger action against the regime of Bashar Assad, the newspaper said.
Meanwhile, U.S. Defense Secretary Chuck Hagel told a Senate panel the Pentagon will send some 200 U.S. soldiers to Jordan to control spillover violence from the Syrian civil war.
But the troops, near Jordan's border with Syria, could be the forerunner of 20,000 or more deployed if the Obama administration decides to intervene in the 2-year-old civil war, senior U.S. officials told the Los Angeles Times.
The 200 or so troops from the 1st Armored Division at Fort Bliss, Texas, will work alongside Jordanian forces to "improve readiness and prepare for a number of scenarios," Hagel told the Senate Armed Services Committee.
Those scenarios could include securing chemical weapons arsenals or to prevent the war from spilling into neighboring countries, he said.
But the Pentagon has drawn up plans to possibly expand the force to 20,000 or more, the officials told the Times.
These forces could include special operations teams to find and secure Syrian chemical weapons stockpiles, U.S. air defense units to protect Jordan's airspace and conventional military units capable of moving into Syria if necessary, the Times said.
Defense Department officials consider the move as preparing the United States for possible direct military involvement in Syria, the Times said.
The Pentagon had no immediate comment on the report.
"Military intervention is always an option, but it should be an option of last resort," Hagel told the Senate committee.
He warned a major deployment could "embroil the U.S. in a significant, lengthy and uncertain military commitment."
Hagel told the panel the new forces will initially help deliver humanitarian supplies and help the Jordanian military cope with the flood of Syrian refugees.
They will replace an ad hoc group of U.S. troops "pulled from various units and places" who have been in Jordan since last year, he said. That group included U.S. Army Special Forces, also known as Green Berets.
Committee Chairman Carl Levin, D-Mich., asked Hagel and Joint Chiefs of Staff Chairman Gen. Martin Dempsey, who testified with him, if Obama had asked the Pentagon to recommend how to apply "any additional military pressure" on the Syrian regime of President Bashar Assad.
"We've had national security staff meetings at which we've been asked to brief the options, but we haven't been asked for a recommendation," Dempsey said.
"We've not been asked," Hagel said. "As I said, I've not been asked by the president."
Hagel is to be in Jordan next week as part of a Middle East trip that will also take him to Israel, Saudi Arabia, Egypt and the United Arab Emirates, the Pentagon said Wednesday.