Tue Mar 20, 12:03 PM ET

BEIRUT (Reuters) – Lebanon’s Parliament Speaker accused the ruling majority coalition on Tuesday of dealing a crushing blow to talks aimed at ending a political crisis, signaling a rise in tensions in the four-month-old standoff.

 The comments by Nabih Berri, a key opposition leader, came after pro-government legislators gathered inside the parliament building in downtown Beirut to persuade him to convene a session to ratify a U.N.-backed tribunal that would try suspects in former Prime Minister Rafik al-Hariri’s 2005 assassination

The tribunal is a contentious issue between the anti-Syrian government of Prime Minister Fouad Siniora, which wants the court, and the opposition which includes pro-Syrian Hezbollah and a Christian faction. The opposition fears the tribunal may be used as a political tool in its current form.

A U.N. inquiry has implicated Syrian and Lebanese security officials in the killing, though Syria denies involvement

Berri and Saad al-Hariri, son and political heir of the former premier, had held several rounds of talks over the past two weeks which raised hopes for an end to the crisis.

But Berri, speaking at a news conference at his headquarters, said the ruling coalition’s insistence to push through with the court "led to the dealing of a crushing blow to the talks between myself and Saad al-Hariri."

He did not close the door to further talks though, saying "the arm is extended to rescue Lebanon."

Siniora’s government signed an agreement to create the tribunal, but the opposition considers the cabinet illegitimate after Shi’ite ministers resigned in November to protest the premier’s refusal to meet their demands for veto power.

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The tribunal needs to be ratified by parliament to come into force. While parliament started its spring session on Tuesday, Berri is not obliged to convene a session immediately.

"It is possible for me to convene a parliamentary session. And if they had not done this act today, I would have called the session sooner," he said, referring to the gathering of pro-government legislators.

"But now I want to call it later," Berri said.

Hezbollah is backed by Syria and Iran while Saudi Arabia, France and the United States support Siniora and the ruling coalition.

Earlier parliament member and Druze leader Walid Jumblatt called on Berri to hold a session away from "Iranian and Syrian dictations."

"Here is (the place) for dialogue," Jumblatt told reporters upon arrival at the parliament building, near where legislators had gathered. "Here is the place for decisions and laws."

The opposition wants veto power in a national unity government and early parliamentary elections. Its activists have been camped out in central Beirut near Siniora’s headquarters since December 1 to press their demands.

Though he did not rule out the possibility the opposition could escalate the crisis to civil disobedience, Berri said talks were still the only way to resolve the standoff.

"I will negotiate with anyone without exception. If I find anything … which I can use to rescue the talks, I will continue. We have no other option but to negotiate between ourselves."