The order comes at a time when Lebanon faces threats on multiple fronts. Lebanese officials, the Bush administration and the United Nations blame much of the trouble on Syria, which occupied its southern neighbor for nearly three decades before withdrawing troops under international pressure in 2005.

The proclamation signed by Bush bars from the United States those "who have contributed to the breakdown of the rule of law in Lebanon, including through the sponsorship of terrorism, politically motivated violence and intimidation, or the reassertion of Syrian control in Lebanon." The White House released 10 examples of those covered by the ban, including top Syrian government officials.

"This is a tool to demonstrate to Syria our desire for them to stop meddling in Lebanon, to demonstrate to Syria and those who want to destabilize the democratically elected government of Lebanon that we will continue to increase pressure until they suspend their activities," said White House spokesman Gordon Johndroe.

Lebanon has recently been wracked by instability, including a war last summer between Hezbollah militants and Israeli forces, government forces fighting with a radical group in Palestinian refugee camps, and a political impasse with the protesting opposition. The U.N. Security Council voted last month to form a court to try Syrian suspects in the 2005 assassination of former Lebanese prime minister Rafiq al-Hariri. Just weeks after that vote, a car bomb killed a Hariri ally, lawmaker Walid Eido.

A team of U.N. experts this week cited numerous sites along Lebanon's border with Syria where arms can be freely smuggled. The sites include armed Palestinian camps that straddle the frontier. The experts' report expressed suspicion about Lebanese authorities not having intercepted a single arms shipment, suggesting that security forces may be complicit in the trade or, at least, turning a blind eye.

Among those targeted by the White House order are Asef Shawkat, director of Syrian military intelligence, and two other top intelligence officials; Hisham Ikhtiyar, an adviser to Syrian President Bashar al-Assad; and six former members of Lebanon's cabinet or parliament. The former U.N. chief investigator has implicated Shawkat and other members of Assad's inner circle in Hariri's death.

Daily An-Nahar reported today that among the Lebanese targeted by the ban are former ministers Abdul Rahim Morad, Joseph Samaha, Assem Qansou, Asaad Hardan, Wiaam Wahhab and former MP Nasser Qandil.

The paper also metioned that among the Syrians trageted by the ban are leading Syrian intelligence officers Jameh Jameh and Rustom Ghazaleh.

Bush signed the proclamation here, where he is spending time with his parents at the family compound and preparing to host Russian President Vladimir Putin for talks starting Sunday. The president also received briefings on the car bombs found in London and went boating with his father, former president George H.W. Bush. - with Agencies