The United States said Friday it is very concerned about the Hezbollah-led blockade of government offices in Beirut. The State Department called it an effort to topple the democratically elected administration of Prime Minister Fuad Siniora. VOA's David Gollust reports from the State Department.

Officials here say they are deeply concerned by the latest events in Beirut, which they say are part of a long-running effort by Hezbollah, supported by Iran and Syria, to de-stabilize Lebanon.

Hundreds-of-thousands of members of the Iranian-backed Lebanese Shi'ite movement and their supporters surrounded the offices of Mr. Siniora Friday, in an effort to force the resignation of the pro-Western prime minister, and replace the current Cabinet with a so-called unity government, in which Hezbollah would have effective veto power.

At a news briefing, State Department Deputy Spokesman Tom Casey reiterated U.S. support for Mr. Siniora and what he said were his efforts to overcome 30 years of outside domination and occupation of Lebanon.

He said the siege of the prime minister's offices was nothing less than an attempt to overthrow Lebanon's lawful government:

"The demonstrations, as you know, are aimed at toppling Lebanon's legitimate and democratically-elected government, and, certainly, threats of intimidation or violence isn't something that I think anyone would consider a democratic or constitutional mechanism for changing a government," he said.

Lebanese tensions have been rising since early this month, when several Hezbollah and allied Cabinet members resigned after the break-down of talks on giving the Shi'ite movement more power.

The crisis deepened two days later, when the remaining Cabinet approved a U.N. plan for an international tribunal to try those behind the 2005 car bomb attack that killed former Prime Minister Rafik Hariri, an act widely blamed on Hezbollah ally Syria.

It worsened again with the November 21 death of anti-Syrian Cabinet member Pierre Gemayel, whose ambush killing in a Christian area of Beirut brought hundreds-of-thousands of government supporters into the streets.

Spokesman Casey said with events like the Gemayel assassination, it is clear there is a pattern of intimidation of forces aligned with the country's democratic government.

He said the United States remains committed to supporting Prime Minister Siniora and his team, as it rebuilds Lebanese sovereignty through, among other things, implementation of U.N. Security Council Resolution 1701.

Approved in August after the conflict between Hezbollah and Israel, Resolution 1701 calls for the extension of Lebanese government control over the entire country, while reiterating demands in Resolution 1559 of 2004 for the disarmament of remaining militias in Lebanon, including Hezbollah.

Hezbollah, which accuses the Siniora government of corruption and being under U.S. domination, says it will continue its demonstrations indefinitely.

Spokesman Casey said the U.S. ambassador to Lebanon, Jeffrey Feltman, has been in contact by telephone with members of the besieged government, but provided no details.