Fabius Says 'All Options on the Table' after Confirming Sarin Gas Used in Syria, U.S. Says More Evidence Needed

French Foreign Minister Laurent Fabius said Tuesday that Paris had solid proof that President Bashar Assad's regime was using sarin gas in the Syrian conflict, adding "all options" are on the table.

"We have no doubt that the gas is being used..the laboratory tests are clear," he said on television after French laboratory tests on blood and hair samples from Syria pointed to the use of sarin gas.

"There is no doubt that the regime and its accomplices" are using them, he added.

"A line has been indisputably breached. We will hold talks with our partners on what we must do and all options are on the table," to decide "whether to react, including in an armed manner," Fabius said.

"But we are not there yet," Fabius said, referring to armed intervention.

"We must react but at the same time we must not block an eventual peace conference," he said, referring to U.S.- and Russia-backed efforts to get the rebels to join peace talks in Geneva.

Fabius did not give any details of where or by whom the sarin had been used but said it had taken place "several times in a localized manner".

Diplomats said the unidentified samples tested by the French laboratory had come from two locations: a suburb of Damascus and Saraqeb in the northwest of the country.

The samples from near Damascus were brought back to France by two Le Monde journalists who reported the use of chemical weapons in the area in mid-April.

Fabius said he had transferred his results to the United Nations, which is seeking to establish whether chemical weapons have been used in Syria.

Meanwhile, the White House said Tuesday it needed more evidence before declaring formally that sarin gas has been used in Syria.

"We need to expand the evidence we have ... before we make any decision," spokesman Jay Carney said, alluding to President Barack Obama's stated position that use of the deadly nerve agent would be a "game-changer" for Washington.

U.N. investigators said earlier they had "reasonable grounds" to believe both sides in Syria used chemical weapons.