Israel is demanding that U.N. troops patrol the Syria-Lebanon border to prevent Hezbollah from receiving arms shipments. But even if Israel overcomes Syrian objections to the idea, policing the mostly mountainous frontier could prove nearly impossible.

The controversy has developed as the United Nations tries to muster enough peacekeepers to serve as a buffer force between Israeli troops and Hezbollah guerrillas in Lebanon's south.

Israel, which accuses Syria of supplying arms to Hezbollah, refuses to lift its sea and air blockade of Lebanon unless U.N. troops also deploy to the far larger Syria-Lebanon border.

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It's a tall order. Syria borders Lebanon both to its east and north, with four official crossings, including one on the road between Beirut and Damascus. But there are dozens of dirt tracks running between the countries through a mountain range, routes that have been used for centuries by smugglers and many of them able to carry modern-day vehicles.

It's unclear, moreover, how much Hezbollah is in need of a weapons resupply. Although Israel said Hezbollah fired about 4,000 rockets into northern Israel during the 34-day war, the guerrillas were believed to have an arsenal of more than 12,000 of the weapons when the fighting started.

There has also been wide speculation that the Syrian army left behind a huge weapons supply for Hezbollah as it withdrew from Lebanon in April 2005. Hezbollah draws primary backing from Syria and Iran, which established the guerrilla group and its political arm in the Bekaa Valley in 1982.

Syrian President President Bashar Assad on Thursday called Israel's demand a "hostile" move aimed at damaging relations between the neighbors. He said it was unprecedented for international forces to police a border between two countries that have not been at war.

Israeli Foreign Minister Tzipi Livni dismissed Assad's objections Friday, saying Syria must respect Lebanon's sovereignty and an arms embargo imposed on Hezbollah after the war, which ended with an Aug. 14 cease-fire. Syria virtually controlled Lebanon for nearly three decades before its troops pulled out last year and has threatened to close the border if international forces take positions there.

"It's about time that Syria give Lebanon the freedom and ability to be an independent and sovereign state," Livni said in Tel Aviv. "We expect and I believe the entire international community expects the Syrian government to respect the decision of the international community."

Caught in the middle, Lebanese Prime Minister Fuad Saniora said he called U.S. Secretary of State Condoleezza Rice and U.N. Secretary-General Kofi Annan late Thursday to ask for help in lifting Israel's blockade. Lines reappeared at Lebanese gas stations Friday, signaling renewed shortages after a brief respite when a fuel tanker was allowed into the Beirut port.

Although Lebanon has not explicitly rejected the idea of deploying U.N. forces to the Syrian border, Saniora stressed his government has already sent troops there.

"We have no intention of showing any hostility toward Syria," he said. "We want cordial relations with Syria and we are taking care of the issue of the border to prevent any infiltration into Lebanon."

Lebanon's Cabinet called on the international community Thursday to send forces to free up the Lebanese army to patrol its frontiers. It did not directly address the issue of U.N. troops on the Syrian border. Information Minister Ghazi Aridi, however, said the government would ask Germany for technological help in controlling Lebanon's borders.

Four days the cease-fire took effect, the Lebanese army began setting up checkpoints near dozens of illegal border crossings with Syria in a bid to help prevent arms smuggling, a Lebanese military official said Friday, speaking on condition of anonymity because he was not authorized to discuss troop placement. He said the army's plan covered an estimated 60 illegal border crossings.

U.N. envoy Terje Roed-Larsen said Sunday that 2,000 Lebanese soldiers have been deployed so far along Lebanon's eastern border with Syria, with the goal of eventually having 8,600.

The international community has been slow in volunteering troops for the expanded U.N. force, designed to grow eventually to 15,000. European Union foreign ministers were taking up the issue in Brussels on Friday under pressure to get at least vanguard on the ground next week.

About 150 French soldiers — an engineering team — came ashore Friday at Naqoura in southern Lebanon. They joined 250 of their countrymen already in Lebanon and raised to 2,200 the number of U.N. peacekeepers in the south of the country.

On Thursday, French President Jacques Chirac announced his country would increase its contribution to 2,000 troops, saying he had been given assurances by the U.N. concerning the peacekeepers' mandate. He did not elaborate.

There were concerns that peacekeepers would not be able to act robustly enough to protect themselves and carry out their mission, which for now does not include disarming Hezbollah.

Belgium, which had been waiting for clarification on the rules of engagement and security guarantees, announced Friday it would also send troops.

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