ISTANBUL -- After spending seven years in jail for challenging Syrian dictator Bashar Assad and surviving a travel ban of more than a decade, one of the country’s most respected political dissidents has left Damascus and taken up an active leadership role in the fractious resistance movement.

Riad Seif, 66, a businessman turned-politician, flew out of Syria on July 13 after receiving permission for reasons that he said were not explained.

Seif took on both Bashar Assad and his father, Hafez, before him, and paid for his audacity when the government bankrupted his business, suspended his parliamentary immunity and threw him in jail.

When his latest jail term ended in mid-2010, he quit active dissident politics, only to jump back into the fray when revolution swept through the Arab world early last year. He got beaten twice and jailed for another 10 days, but instead of lowering his profile, became the only representative in Damascus of the Syrian National Council, the group Washington recognizes as an umbrella for anti-Assad opposition.

Now ailing with prostate cancer and recovering from a heart operation, he made clear in an interview with McClatchy that he has no intention of quitting as long as his health allows.

And in one of his first actions following an operation in Germany to open a nearly closed heart vein, he flew to Moscow with other SNC leaders in early July. There he told Russian leaders that they had to change their policy and drop Assad, accusing them of responsibility for the deaths of as many as 20,000 civilians. He said that Russia and China could quickly bring down Assad if they’d stop vetoing U.N. resolutions that threaten tough sanctions.

“I told Lavrov that the Russians are really responsible for the deaths of Syrians,” he told McClatchy in a series of interviews here, referring to Russian Foreign Minister Sergey Lavrov. “Russians are partners in the killings.“

Lavrov “was angry” but “of course he was diplomatic.” Seif recalled. “He didn’t answer.”

Seif didn’t let up.

“I told Lavrov, ‘Imagine your army is shelling your city in Russia. What will you do?’ ” Seif recounted. “They are destroying cities everywhere on the heads of our people.”

On Thursday, Russia and China vetoed a Security Council resolution that would have called for sanctions if Syria did not pull its heavy weaponry out of residential neighborhoods. The Russians said the proposed resolution would have amounted to backing the rebels in the ongoing violence.

Seid has a track record that few in the resistance movement can match -- a popular politician, a proponent of democratic change, and a manager who was a successful garment manufacturer. In the context of a leadership that is colorless, inaccessible, slow to respond, divided by rivalries and hard-put to raise funds, the low-key Seif is a man of charisma.

He is not a self-promoter, and his talk with McClatchy was his first extensive interview in many years.

Seif is convinced that Assad would quickly meet his end if Russia stopped backing him because Syrians have made their minds up.

“Whatever price the Syrians will pay, they will pay not to have Assad as the president,” he said. “Many people have lost everything, but they do not feel sorry for what has happened. They say, ‘That is the price of freedom and dignity’.”