Hezbollah's secretary general has called the US-backed tribunal probing the assassination of former Lebanese prime minister as an "American-Israeli project."

In a speech on Sunday night, Seyyed Hassan Nasrallah said Israel is relying on the tribunal that is trying to indict Hezbollah members.

The US-sponsored tribunal is reportedly about to indict some Hezbollah members in the 2005 assassination of former Lebanese Premier Rafiq Hariri -- an allegation which is rejected by the Lebanese resistance movement.

Nasrallah also defended the resignations of opposition ministers, which led to the collapse of Lebanon's unity government on Wednesday.

He said the move was constitutional, adding that the 11 ministers stepped down because the government was incapable of confronting the repercussions of the US-backed tribunal.

According to Nasrallah, the ruling party came to power by buying votes.

Meanwhile, Nasrallah underscored that the opposition cannot keep silent towards a movement that supports false witnesses.

The Hezbollah chief also said Lebanon has found itself in the current crisis due to pressure applied by the US and Israel among other forces.

Saudi Arabia and Syria had unsuccessfully joined hands to pull the country out of the situation. Nasrallah said Washington and Tel Aviv had prevented the joint endeavor from bearing fruit, thus propelling Beirut into the current situation.

"Why did all of this happen? Why did we reach this stage?" he asked.

The Hezbollah leader blamed Caretaker Prime Minister Saad Hariri for the end to the Arab initiative that was an alternative to the tribunal.

"First of all, it is very clear that the Americans and the Israelis rejected from the very beginning, these Arab efforts, these Saudi-Syrian efforts... They let the joint endeavor continue for some time as they did not suspect it to bear fruit", the Hezbollah secretary general, said.

However, once they found out that the issues are "heading positively," they intervened "very decisively and they informed the Saudis and Syrians that these efforts cannot continue," Nasrallah asserted.

He also said some Lebanese politicians had a role to play in the stonewalling of the Saudi-Syrian initiative.