Beirut, Lebanon (CNN) -- Members of the powerful Hezbollah movement and its allies brought down Lebanon's unity government Wednesday after resigning from Prime Minister Saad Hariri's Cabinet.

Minister of State Adnan Sayyed Hussein turned in his resignation along with 10 members of the Hezbollah-led March 8 alliance, meaning that the threshold needed -- 11 resignations from the 30-member Cabinet -- to collapse the government had been reached.

Hariri was meeting with President Barack Obama at the White House as the political crisis erupted in Lebanon.

"The efforts by the Hezbollah-led coalition to collapse the Lebanese government only demonstrate their own fear and determination to block the government's ability to conduct its business and advance the aspirations of all of the Lebanese people," Obama said.

Hariri next heads to Paris, where he is expected to meet with French President Nicolas Sarkozy, Hariri's office said.

Lebanon's government has been at an impasse over the U.N.-backed special tribunal's investigation of the assassination of Rafik Hariri, the current premier's father. It is widely expected the tribunal will indict members of Shiite Muslim Hezbollah, which is designated as a terrorist organization by the U.S. State Department.

U.S. Secretary of State Hillary Clinton, in Doha, Qatar, for a Middle East forum, said the tribunal was on the verge of handing down indictments.

"We view what happened today as a transparent effort by those forces inside Lebanon as well as interests outside Lebanon to subvert justice and undermine Lebanon's stability and progress," she said.

Hezbollah has blamed Israel for the 2005 bombing that killed Hariri and has pressured the government to reject the tribunal's probe.

Opposition member Fadi Abboud said the opposition bloc had been calling for a Cabinet session to discuss the tribunal and met Wednesday to discuss what action to take if their demands were not met.

Attempts to resolve the dispute have failed so far. Hezbollah's walkout Wednesday came after a Saudi-Syrian initiative hit a dead end.

In a statement issued before the resignations, Hariri said that "despite the developments in the last hours, we will by all means work to keep the doors open for the Lebanese to reach the solutions that ensure stability and calm and preserve national unity."

Obama stressed to Hariri the importance of the tribunal's work "as a means to help end the era of political assassinations with impunity in Lebanon."

The failure to break the impasse between Hariri's government and Hezbollah has raised fears of a renewal of the sectarian bloodshed that plagued Lebanon in 2008.

Rafik Hariri's death stunned the nation and prompted tens of thousands to protest, blaming neighboring Syria for the killing. Syria has always denied the accusations.

At the time of the bombing, Syria had immense political influence in Lebanon.

A U.N. Security Council resolution demanded Damascus fully cooperate in the investigation. Eventually, the horrific events and the probe led to a complete withdrawal of Syrian troops from Lebanon after 30 years of military presence.

CNN's Nada Husseini and Jill Dougherty contributed to this report.