By Khaled Yacoub Oweis

DAMASCUS (Reuters) - Syria's leading dissident said on Sunday U.S. efforts to improve ties with Damascus could help democratic reform in his homeland.

Riad al-Turk, 79, told Reuters in a rare interview that U.S. President Barack Obama's initiative could also undermine what he called an "unconvincing alliance" between Syria and Iran.

Although arrests of opposition figures have continued despite U.S.-Syrian diplomatic contacts, mending relations between the two countries would make it difficult for Damascus to crush dissent, Turk said.

"The rapprochement helps stabilize the Middle East and puts pressure on the Syrian regime to improve its policies," he said.

"It could be difficult for the regime to change its attitude toward Lebanon or Iraq and its role in the region without improving ties with its own society," he added.

Such improvements would help reform, said Turk, who spent around 18 years in solitary confinement as a political prisoner under the rule of President Bashar al-Assad's father, the late Hafez al-Assad.

"The regime would no longer be able to justify internal policy by talking about external dangers," said Turk.

The United States started talking to Syria shortly after Obama took office in January, departing from a policy of isolation under his predecessor, George W. Bush.

Bush imposed sanctions on Damascus for what Washington described as Syrian support for insurgents in Iraq, its role in Lebanon and backing for militant groups such as Hezbollah -- also backed by Iran.

The United States hopes that by talking to Syria and supporting efforts to resume peace talks between the Damascus government and Israel, Assad would break away from Iran.

OPPOSITION ALLIANCE

Undaunted by age, the scars of prison and six surgical operations, Turk remains the leading opponent of the Baath Party's monopoly on Syria's political system.

He has worked to spread democratic thought and maintain a broad opposition alliance known as the Damascus Declaration, after 12 of its younger members were arrested in late 2007 and sentenced to two-and-a-half years in jail each.

Senior U.S. officials have visited Damascus twice this year since March, but the talks have not prevented Syrian authorities from pursuing a campaign of arrests against dissidents.

Turk said he was under no illusion that Syria's ruling elite might resist change, but ordinary Syrians also stand to benefit from a normalization of ties with Washington that helps revive Syria's battered economy and unhook the noose of sanctions.

Among high profile Syrian figures to be convicted recently of political crimes was Meshaal Tammo, an advocate of Kurdish self-determination who was sentenced this month to three-and-a-half years jail for "weakening national moral."

Michel Kilo, a leading writer, served a three-year term on the same charge and was released around 10 days ago.

"Kilo said that jails do not change convictions. Ruthlessness only undermines the regime," Turk said.

Turk was jailed after he refused to strike deals with Hafez al-Assad and criticized Syria's armed intervention in Lebanon and a crackdown on Muslim fundamentalists that culminated in thousands of deaths.

Turk spent 15 months more in prison for leading the Damascus Spring, a period dominated by calls for democratic reform that lasted almost a year after Bashar succeeded his father in 2000.

Bashar took limited steps to open the economy but made it clear political reform was not a priority with Syria under U.S. pressure, which he said threatened national cohesion.

Turk welcomed Obama's commitment to seeking peace between Syria and Israel, and between Israel and the Palestinians. But he said the two tracks should go hand in hand and warned that peace alone would not guarantee Middle East stability.

"Since Israel was created in 1948, Arab countries, with the exception of Lebanon, have only been ruled by tyrannies that shattered their societies through terrorism, corruption and plunder," he said.

"The crisis in the region cannot be solved without moving from tyranny to freedom and the rule of law."

Turk urged Syria to mend ties with Egypt and Saudi Arabia, as well as boost an Arab peace initiative launched at an Arab summit seven years ago that offers Israel normal relations in return for full withdrawal from occupied Arab land.

"Iran would no longer use the Palestinian-Israeli conflict to its own ends if a solution is reached," he said.

"Syria must not allow any compromise with Israel to come at the expense of the Palestinian cause and to the advantage of the racist government in Israel, which just wants to cause delays."

(Editing by Charles Dick)