Syria has scattered its stockpile of chemical weapons to as many as 50 sites in a bid to complicate US efforts to track them, the Wall Street Journal reported Thursday.

A secretive Syrian military unit had been given responsibility to shift the arsenal of poison gases and munitions, raising questions about the viability of a Russian plan to secure the weapons, the report said, citing US and Middle Eastern officials.

Officials also told the paper it could complicate a possible US military strike on Syria over the Damascus regime's alleged use of chemical weapons.

Washington alleges that more than 1,400 people, including more than 400 children, were killed in an August 21 attack involving poison gas.

US defense officials told AFP the regime appeared to have dispersed some of its chemical weapons in the past few weeks but said the move had not caused serious concern at the Pentagon about the effectiveness of possible US military action.

The two officials, who spoke on condition of anonymity, did not confirm the report that the stocks had been shifted to as many as 50 sites.

"They're dispersing all of their military equipment and material in anticipation of a possible attack," said one official.

"In monitoring the main (chemical weapons) sites, which are less than a dozen, we had noted some activity a little while back," but not in the past few days, a second official said.

He added that the US government did not know precisely where all of Syria's chemical stocks were located.

The Journal reported that the Syrian military's "Unit 450" has been moving the stocks around for months and as recently as last week, according to officials and lawmakers.

Starting about a year ago, the deadly weapons -- traditionally kept at several sites in western Syria -- began being dispersed to nearly two dozen major sites, it reported.

According to the Journal, the unit has also started using dozens of smaller sites, with Washington now believing that the weapons have been dispersed to as many as 50 spots in the country's west, north and south, as well as new sites in the east.

Despite the redistribution, both US and Israeli intelligence agencies still believe they know where most of the weapons are situated, according to the Journal.

However, it quoted one official as saying "we know a lot less than we did six months ago about where the chemical weapons are."

While Washington is employing satellites to track vehicles used by the unit, the pictures don't always indicate what they are carrying, the paper reported.

President Bashar al-Assad confirmed for the first time Thursday that Syria plans to give up its chemical weapons as the United States urged him and his Russian allies to quickly make good on his promise.

But the long-time leader cast fresh doubt on how committed he is to a hastily-hatched plan to secure his country's poison gas stocks by demanding that Washington first drop its threat of military action against his regime.