BEIRUT: The Hezbollah-led opposition's challenge to the Beirut government is a blow to US Middle East policy and shows Washington has limited options to head off Syrian and Iranian influence in Lebanon.

With mounting calls for Washington to engage with Tehran and Damascus as part of its policy to ease violence in Iraq, both states aim to strengthen their hand by dealing the United States a political blow in Lebanon, analysts say.

The United States has accused Tehran and Damascus, acting through Hezbollah, of trying to mount a coup against the government of Prime Minister Fouad Siniora, which came to office after the withdrawal of Syrian troops from Lebanon last year.

Washington and Paris led pressure for the pullout and have forged an alliance with the anti-Syrian majority coalition.

With the United States bogged down in Iraq, Iran and Syria are now seizing a chance to further erode Washington's regional position through Hezbollah's challenge to the government, the analysts say.

Hezbollah and its allies are staging street protests to press their demand for a new government after the collapse of talks on giving them a greater say in cabinet last month.

“It's really squeezing US policy into a corner,” said Oussama Safa, head of the Lebanese Centre for Policy Studies.

“This is definitely a blow for US policy in Lebanon and another way to force on the agenda a change of course in US policy. If they succeed in toppling the government or in paralysing the country, there's nothing the US or the government it backs can do,” he said.

The United States has underlined its backing for the Lebanese government since the Nov 21 assassination of anti-Syrian cabinet minister Pierre Gemayel, pledging more military aid and other support.

But Syria and Iran may hold the most powerful cards in Lebanon through their alliance with Hezbollah -- the strongest faction in the country which claimed victory over US ally Israel in a war in July and August.

Hezbollah accuses some members of the anti-Syrian majority of failing to support it during the war, which was triggered by the capture of two Israeli soldiers on July 12. Hezbollah says its political rivals wanted Israel to destroy their group.

Instead it emerged from the conflict with more political momentum, which Iran and Syria now aim to exploit.

“Syria and Iran are very effectively and very openly trying to assert influence in Lebanon and having a great deal of success,” said Andrew Exum, research fellow at The Washington Institute for Near East Policy.

“There's a high degree of frustration in Washington because events in Lebanon are largely out of American control and expose the limit of American political power in the region.”

Prominent anti-Syrian leaders in Lebanon say Hezbollah aims to pull Lebanon firmly back into a Syrian sphere of influence.

Hezbollah says it wants to topple what it calls a US puppet government in Lebanon so that the opposition can have a real say in how the country is run.

“Both Iran and Syria believe that the current government in Lebanon is vulnerable,” Lebanese political scientist Sami Baroudi said. “They believe that the United States is not in a position to do much to help it. So they feel that there is an opportunity to be on the offensive.”

Iran has been under Western pressure over its nuclear programme while Syria is facing the prospect of an international tribunal to try suspects in the assassination of former Lebanese Prime Minister Rafik al-Hariri.

Although Damascus has denied involvement in the killing last year, an international inquiry into the assassination has implicated Lebanese and Syrian security officials.

Anti-Syrian leaders say Hezbollah wants to bring down the Lebanese government to derail the tribunal and protect their allies in Damascus.

Damascus could be hoping Washington will trade Syrian cooperation in Iraq for a reassertion of its role in Lebanon.

That is what happened in 1990 when the United States acquiesced in the Syrian campaign to defeat Christian leader Michel Aoun in return for support against Saddam Hussein, who had invaded Kuwait. Aoun is now allied with Hezbollah.

The outcome was Syrian dominance in Lebanon for the next 15 years, analysts say. But Washington cannot afford to give way this time, even if it has limited means to fend off the Syrian-Iranian challenge.

“For them to give up Lebanon to Syria because of Iraq would mean giving up on their only diplomatic success in the region over the last six years,” Exum said.—Reuters