Syria denied on Thursday accusations by the White House that it was seeking to topple Lebanon's Western-backed government, and said it was not interfering in Lebanese internal affairs.

"The U.S. administration's attempts to circulate that Syria, Iran and Hezbollah are seeking to destabilize Lebanon are not true," the Syrian Foreign Ministry said in a statement. "Since it withdrew its troops from Lebanon, Syria has voiced its support for anything that the Lebanese agree on through their national dialogue," the statement said.

White House spokesman Tony Snow on Wednesday said there was "mounting evidence that the Syrian and Iranian governments, Hezbollah, and their Lebanese allies are preparing plans to topple Lebanon's democratically elected government." His comments came as Hezbollah's leader stepped up pressure on the Lebanese government for a Cabinet change.

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While the White House did not detail evidence, it singled out Syria for an alleged plan to derail possible prosecutions for the assassination of Rafik Hariri, Lebanon's former prime minister who had tried to draw his country away from Syrian domination.

Local and international pressure following his Feb. 2005 assassination forced Damascus to pull out its troops from Lebanon, ending a 29-year-military presence.

Hezbollah also denied the White House accusations, and the Lebanese parliament speaker — a guerrilla ally — voiced suspicion about America's intentions with such statements.

The guerrilla group accused Washington of interfering in Lebanese politics by trying to shore up Prime Minister Fuad Saniora's government.

Hezbollah is threatening street protests to force early elections in Lebanon if its demands are not met for a "national unity" Cabinet that would give the Islamic militants and their allies veto power over key decisions.

The bold move reflects the Shiite group's push to consolidate the political power it gained following its self-proclaimed victory in its punishing summer war with Israel. The effort seems certain to further exacerbate an already tense political situation in Lebanon, where the government has refused earlier Hezbollah calls to step down and allow the formation of a new Cabinet.

It could also lead to violence, with pro-government groups warning of a confrontation with militants in the streets.

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Wednesday night, a rifle-fired grenade hit a major police barracks in west Beirut, causing damage but no casualties, witnesses and police said. It was the second grenade attack on the same barracks in recent weeks. Another Beirut police station and a downtown building near U.N. offices were also hit in similar attacks last month, which injured six people.

Lebanon's government blamed those attacks on unknown elements aiming to destabilize the security situation after last summer's Israel-Hezbollah war.

On Monday, Terje Roed-Larsen, the top U.N. envoy for Syria-Lebanon issues, and the U.S. ambassador to the United Nations, John Bolton, accused Syria and Iran of violating a U.N. embargo meant to keep Hezbollah from rearming after the 34-day war it waged with Israel.

Roed-Larsen said that representatives of the Lebanese government "have stated publicly and also in conversations with us that there has been arms coming across the border into Lebanon."

The Lebanese government denied having shared such allegations.

"These comments are inaccurate," Lebanese Defense Minister Elias Murr said late Wednesday of Roed-Larsen's statement.

Lebanese Prime Minister Fuad Saniora also weighed in earlier Wednesday on whether his government had informed the U.N. envoy of the alleged smuggling.

"Neither the government, nor I told anybody about this," he told reporters.

Israel has said weapons smuggling for the Iranian- and Syrian-backed Hezbollah guerrilla group was continuing despite an international arms embargo. The government said overflights of Lebanon by its military aircraft was necessary to monitor the situation.

An internal Israeli military document says the air force's controversial flights were also intended in part to pressure the international community to take action to stop arms smuggling and release two abducted Israeli soldiers, a senior Israeli Defense Ministry official said Thursday.

The Lebanese government has deployed thousands of soldiers on the border with Syria to stop smuggling. A U.N. maritime force led by Germany is patrolling the Mediterranean off Lebanon to enforce the embargo.

A state-run newspaper in Syria, Tishrin, on Wednesday rejected the claims about arms shipments into Lebanon from Syria.

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