Syrian refugees
© Galiya Gubaeva/UNHCRRefugees are pouring over the border into Iraqi Kurdistan

The CIA is supervising fresh weapons consignments from Saudi Arabia and other Arab states to Syria's rebels to help them to capitalise on a US bombing offensive that could start next week.

Free Syrian Army co-ordinators in the Gulf say they are in urgent talks with Arab states to secure fresh shipments of anti-tank weapons, surface-to-air missiles and conventional small arms. With American air cover, the rebels are intent on taking advantage of the first period of air superiority they have had during the 30-month conflict.

One Syrian opposition representative said: "We are talking to our Arab allies and working on the Syrian border to get this done. This is a one-off opportunity and we have to make it count."

Security sources in the Gulf confirmed the Saudi plans, which are being co-ordinated with Qatar, Turkey and Jordan and overseen by the CIA.

Washington's Arab allies, especially Saudi Arabia, which is the linchpin of Arab efforts to arm and finance the rebels, were initially dismayed by President Obama's unexpected decision to defer to Congress last week for approval for the strikes. Riyadh has been pushing for months for US intervention.

However, with Congressional approval for up to three months of attacks on Syria potentially just days away, the rebels believe that they have a greater opportunity than expected to make gains while the regime's artillery and air force are suppressed.

On Wednesday, the Senate Foreign Relations Committee passed a resolution calling for a "change in momentum on the battlefield".

The White House authorised the CIA to help arm the rebels in June, but the agency has yet to do so itself amid concerns that weapons could fall into the wrong hands. However, US agents at forward bases on the borders of Syria have final oversight on most large arms shipments into rebel-held territory.

Saudi Arabia has consistently denied arming the rebels, but Bandar bin Sultan al-Saud, its intelligence chief, has been shuttling to Washington for weeks pressing for action. Riyadh has also been urging the Arab League to support military intervention.

Under Prince Bandar's supervision, the kingdom has taken control of arms shipments to the Syrian rebels across the Jordanian and Turkish borders. To allay Western concerns, Saudi intelligence and the CIA have sought to keep a tight rein on the supplies, stepping up efforts to ensure that weapons are passed to approved rebel groups rather than affiliates of al-Qaeda.

These jihadists, many of them battle-hardened from campaigns in Afghanistan, Chechnya and North Africa, have spearheaded the rebel offensive on several fronts but have splintered the opposition, clashing with FSA groups and civilians as they seek to carve out turf for themselves, seizing towns and imposing Islamic law.

These groups will also benefit from the window of opportunity provided by US airstrikes. "This will level the playing field for all opposition groups. The downside is that affiliates of al-Qaeda get the same advantage," Theodore Karasik at the Institute for Near East and Gulf Military Analysis in Dubai, said.

Saudi officials are wary of this threat. One official in Riyadh said that despite the increased arms shipments and the kingdom's determination to cleave Syria away from Iran and Hezbollah, Saudi Arabia did not wish to topple President Assad immediately and risk allowing extremists to seize power. Instead, Riyadh aims to squeeze the Assad regime. "If Bashar [al-Assad] fell tomorrow there would be chaos," one Saudi official said. "The Islamists could seize Damascus. It is just as important to the kingdom and its allies to manage the transition of power, when it happens."

After losing ground to the regime throughout the summer, rebel forces have made no secret of their plans to capitalise on the US intervention. Several battles around Syria hang in the balance, including in the suburbs of Damascus where chemical weapons were allegedly used.

The delay from the White House has been criticised for granting the Syrian regime time to secure critical hardware and supplies in hardened bunkers so that it can ride out the anticipated wave of American attacks and counter-attack when it is over.

Some analysts believe that, given the broader scope of the operation now being pplanned, the added time could be beneficial, with US, European, Arab and Israeli intelligence drawing together detailed analysis of regime targets. "The same applies to those supporting the rebels," said Mr Karasik. "They have more time to redraw battle plans, gather intelligence and increase reconnaissance of potential targets."

US intelligence sources declined to comment on "purported operations".