Israeli Prime Minister Ehud Olmert is too weak to take the necessary steps for peace with Syria, Hamas' exiled leader said Saturday during a visit to Iran, the militant group's ally.

An investigation into Olmert over corruption allegations has raised doubts about his ability to conclude a peace deal with the Palestinians by a year-end target or pursue recently confirmed peace talks with Syria.

Hamas leader Khaled Mashaal said there is skepticism about the seriousness of Israel to return the Golan Heights to Syria. Withdrawing from the strategic plateau that Israel captured in 1967 is Syria's key demand for peace. But it would be tough to sell in Israel and unlikely that the unpopular Olmert would be able to pull it off.

"It's maneuvering and playing with all the (negotiating) tracks — it's a well known game and besides, Olmert's weakness will not allow him to take this step," Mashaal said.

Mashaal spoke during a joint news conference with Iranian Foreign Minister Manochehr Mottaki, in response to a question about Wednesday's announcement that Israel and Syria had restarted direct peace negotiations.

Mashaal, who resides in the Syrian capital, Damascus, was careful not to criticize Syria's decision to restart negotiations with Israel and said he was sure the renewed talks would not come at the expense of the Palestinians.

Israel has asked Syria to cut its ties with Hamas and Iran as a condition for any peace agreement, which Damascus rejected Saturday.

An editorial in the Syrian Tishrin newspaper, which reflects official policy, said Israel could not lay down preconditions ahead of negotiations.

"Damascus does not want preconditions, that would put the cart before the horse ... It does not bargain over its relations with other countries and people, nor would it want to bargain with others over their relations," the editorial said.

Israel and Syria are bitter enemies whose attempts at reaching peace have failed in the past. The last round of talks collapsed in 2000 because of a disagreement over a narrow strip of land along the Sea of Galilee that Israel wanted to keep to preserve its water rights.

The two countries have fought three wars, their forces have clashed in Lebanon, and more recently, Syria has given support to Hezbollah guerrillas in Lebanon and Palestinian militant groups including Hamas. Iran, Israel's archenemy, also backs Hezbollah and Hamas.

During the news conference, Mashaal also renewed his condemnation of the Israeli-led blockade of the Gaza Strip, imposed after Hamas overran the coastal territory a year ago. He also threatened to forcibly reopen Gaza's Rafah crossing to Egypt.

"If the international community and the concerned parties don't take the initiative and break the siege, we will break it ourselves. We insist on opening all crossings, particularly Rafah," he said.

In January, Hamas militants blew holes in the wall separating Gaza from Egypt, sending a flood of desperate Palestinians across the border to buy supplies.

Egypt resealed the border 12 days later and has warned Hamas against a repeat performance.