Faisal al-Qudsi, the son of a former Syrian president, told the BBC the military action could only last six months and then there would be “millions of people on the streets”.
But he said President Bashar al-Assad’s government would fight to the end.
The 11-month uprising against Mr Assad has claimed thousands of lives.
Human rights groups have put the figure at more than 7,000, while the government says at least 2,000 members of the security forces have been killed combating “armed gangs and terrorists”.
The violence continued on Saturday, when Syrian troops fired on mourners during a funeral that turned into a mass demonstration in Damascus. Activists say at least one person was killed there and some 20 across the country.
Speaking to the BBC’s Weekend World Today programme, Mr Qudsi said the economy had been crippled by sanctions and that although Iran was sending money, it was not enough.
Mr Qudsi now chairs a London-based investment banking firm and has been heavily involved in private sector investment in Syria.
He said the uprising had destroyed tourism and the sanctions on exports of oil and other products had dramatically reduced the gross domestic product.
“So, effectively the foreign exchange reserves of the central bank have come down from $22bn (£14bn) to about $10bn and it is dwindling very rapidly,” Mr Qudsi said.
He said the military phase against protesters could only last another six months “because the army is getting tired and will go nowhere”.
“They will have to sit and talk or at least they have to stop killing. And the minute they stop killing, more millions of people will be on the streets. So they are in a Catch 22.”
He added: “The apparatus of the government is slowly disintegrating and it’s almost non-existent in trouble spots like Homs, Idlib, Deraa. Courts are not there; police are not interested in any sort of crime and it is affecting the government very, very badly.”
But Mr Qudsi said Mr Assad would fight to the end because he and his supporters think there is “a universal conspiracy against the government of Syria”.
Meanwhile activists say government forces continue to build around the city of Homs, with shelling of the district of Baba Amr resuming on Sunday, targeting hundreds of opposition fighters holed up there.
Our correspondent, Jim Muir, says human rights groups fear a massacre there if a full ground assault is launched.
Also on Sunday, the Sana news agency reported that gunmen had opened fire on a car carrying two key officials in the northern state of Idlib, prosecutor Nidal Ghazal and judge Mohammed Ziadeh, killing both of them and their driver.
Activists said state security forces had opened fire on the car.
Meanwhile UK Foreign Secretary William Hague again called for President Assad to step down.
He said he feared the country was “going to slide into a civil war” and criticised Russia and China for failing to back a UN Security Council resolution.
Egypt on Sunday became the latest country to withdraw its ambassador from Syria, “until further notice”.
Violence has continued across the country despite the presence in Damascus of Chinese envoy Zhai Jun.
Mr Zhai met several opposition figures in the capital on Saturday, but our correspondent says one told Mr Zhai that although they were ready for dialogue if it were serious, they believed the regime had lost all credibility.
Our correspondent says the violence at Saturday’s funeral in Mezzeh, on the edge of Damascus, was serious as it was so close to the centre of government.
The shooting occurred at a funeral for people killed during a protest against President Assad on Friday.
The funeral procession turned into one of the biggest demonstrations the capital has seen, with thousands of people chanting slogans calling for an end to the Assad regime.
Syria restricts access to foreign media and it is often not possible to verify some reports and casualty figures.
Mr Zhai had earlier held talks with President Assad.
Mr Zhai called for all sides to end the violence immediately.
Mr Assad is pressing on with his plan for a referendum on a new constitution, followed by elections.
However, the opposition has called for a boycott of the 26 February referendum, saying it cannot be held while violence continues.