Saudi Arabia offered to buy billions of dollars worth of arms from Russia in return for a Moscow commitment to ease its support for Syrian President Bashar Assad and to not block any future United Nations Security Council resolutions against the Damascus regime.

According to a Wednesday report from Reuters, based on several unnamed sources from across the Middle East, Saudi Intelligence Chief Prince Bandar bin Sultan made the proposal to Russian President Vladimir Putin when the two met in Moscow last week.

Syrian opposition sources claim Bandar offered to buy $15 billion worth of weapons and also pledged to ensure that Gulf gas producers will not challenge Russia’s position as the leading gas supplier to Europe.

A Lebanese source told Reuters that at the end of the four-hour meeting “the Saudis were elated about the outcome.”

Neither Russian nor Saudi officials publicly confirmed the report. Russia has remained Assad’s staunchest ally during the two-year-long civil war that has killed over 100,000 people.

However, an unnamed Western diplomat was pessimistic about the likelihood that Russia would give up its influential position in the region in return for even such a lucrative arms deal. The diplomat told Reuters that Russian officials are also wary about whether the Saudis have a coherent plan for maintaining stability in a post-Assad Syria.

A senior Syrian opposition figure said there had been a “build-up of Russian-Saudi contacts prior to the meeting.”

“Bandar sought to allay two main Russian fears: that Islamist extremists will replace Assad, and that Syria would become a conduit for Gulf, mainly Qatari, gas at the expense of Russia,” he said. “Bandar offered to intensify energy, military and economic cooperation with Moscow.”

According to the report, it was Russia that persuaded Assad to allow UN investigators to begin looking into the suspected use of chemical weapons that both sides blame on each other.

The UN gave a green light for the investigation last week following an “understanding” reached between the Syrian government and UN disarmament chief Angela Kane and Sellstrom who visited Damascus at the end of July.

The team will visit the village of Khan al-Assal, a village on the southwestern outskirts of the embattled city of Aleppo, which was captured by the rebels and was under attack by government forces last week. The government and rebels accuse each other of being behind a purported chemical attack on the village on March 19 that killed at least 30 people.

Reuters said that in 2008 Russia agreed to sell Saudi Arabia 150 T-90 tanks along with 100 Mi-17 and Mi-35 attack helicopters and additional BMP-3 infantry fighting vehicles, but although signed and sealed, the deal never went through.