Beirut, Lebanon - The U.S. ambassador to Lebanon Jeffery Feltman on Wednesday rejected suggestions that a push for greater democracy in the country would compromise Lebanese security.

"The United States does not support any efforts, any deals or any promises to trade away Lebanon's sovereignty in return for stability through foreign interference," Feltman said in a written statement.

"Only full sovereignty can guarantee Lebanese security and provide fertile ground for democracy to take root," Feltman said.

The ambassador also called on Syria, the former powerbroker in Lebanon, to cooperate with the U.N. probe into the murder of former prime minister Rafik Hariri.

"The United States expects Syria to implement fully its international obligations," Feltman said.

"No deal can lighten or eliminate the requirement for unconditional Syrian cooperation," he added.

Since Hariri was assassinated in a car bomb in February last year, the security situation in Lebanon has sharply deteriorated, with a series of blasts targeting anti-Syrian officials and journalists.

Wednesday"s statement by Feltman coincided with a statement by U.S. Secretary of State Condoleezza Rice threatening to refer Syria to the U.N. Security Council again if it continued to obstruct the Hariri investigation.

Rice accused Damascus of hampering the probe into Hariri"s assassination.

"The United States has grave and continuing concerns about Syria"s destabilizing behaviour and sponsorship of terrorism," she added.

She said Syria has "failed" to implement five U.N. Security Council resolutions over the assassination of Hariri in 2005.

The Syrians were widely blamed by the anti-Syrian Lebanese opposition of being behind the Hariri murder. Local and international pressure forced Syria to end almost three decades of military presence in the country in 2005. (with DPA)