Washington: The Syrian regime has prepared aerial bombs loaded with deadly nerve gas that could be dropped on Syrian rebel strongholds, the American NBC network reported on Wednesday.

The Syrian military is awaiting final orders from President Bashar Al Assad, unidentified US officials told NBC News. Officials said on Tuesday there was no evidence that the process of mixing the two chemicals that together make sarin gas, but on Wednesday the nerve agents were locked and loaded inside the bombs.

Sarin is a deadly agent that can kill tens of thousands of people within minutes if released in a densely populated area.

If confirmed, the move would mark a step further in Syria’s progression toward possible use of chemical weapons.

US officials told NBC News that the loaded aerial bombs could be dropped onto the Syrian people from dozens of fighter jets.

The US officials quoted by NBC stressed that the sarin bombs had not been loaded on to planes. One of the officials said if he were to do so, “there’s little the outside world can do to stop it.”

Meanwhile, the US Senate has recommended that President Barack Obama study the possibility of imposing a no-fly zone over Syria.

In an amendment approved on Wednesday, the senators to require the Pentagon to report on options for using US military assets to prevent Syrian President Bashar Al Assad from using air power against opposition forces.

“This amendment is simply a way of saying we in the Senate are concerned, care about the slaughter going on in Syria and agitated that those in the rest of the world are not doing more,” senator Joseph Lieberman said.

The US administration earlier said it opposed the move. The White House said, however, that it was ready to study all options for ending the Syrian conflict.

CNN reported that the Israeli, Jordanian, Lebanese and Turkish intelligence services were in close contact with their US counterparts to decide on the next steps.

The disposition of Syria’s chemical stockpiles is an especially sensitive issue in Israel, with its close proximity to Syria, leaving it potentially vulnerable to Syrian ballistic missiles and warplanes.

Western and Israeli officials are believed to be closely monitoring known Syrian chemical weapons depots. An unanswered question is whether signs of a rebel approach on a chemical facility would trigger an international response to prevent toxic weaponry from falling into the hands of insurgent militias. The fragmented Syrian rebel force includes Islamist units and several brigades said to be linked to Al Qaida. Israel believes that Al Assad took steps to keep chemical weapons out of the hands of militants. Israel’s vice-prime-minister, Moshe Yaalon, told Israeli media that “clear messages were relayed to Assad on a number of opportunities, and in response Al Assad in fact gathered up the weaponry and separated the material.”

Earlier on Wednesday in Brussels US Secretary of State Hillary Clinton repeated US concerns that the Syrian regime could use chemical weapons.

“Our concerns are that an increasingly desperate [Al] Assad regime might turn to chemical weapons or might lose control of them to one of the many groups now operating in Syria,” she told reporters.

She said the regime’s fall was only a matter of time and renewed her call for a political transition in Syria, urging Al Assad to step aside.

The Syrian government, fighting to prevent the capital Damascus from falling to rebel forces, has insisted it would never resort to chemical weapons.

US President Barack Obama issued a warning to Damascus on Tuesday, saying any use of chemical weapons against the rebels fighting the regime would not go unanswered.

“The world is watching,” Obama said. “The use of chemical weapons is and will be totally unacceptable. If you make the tragic mistake of using these weapons, there will be consequences, and you would be held accountable.”