BEIRUT - Syria's civil war spilled over into neighboring Lebanon again Sunday, with gun battles in the northern city of Tripoli between supporters and opponents of President Bashar al-Assad's regime that left four dead.

Nine Syrian judges and prosecutors also defected to the opposition. It was the latest setback for the regime, which appears increasingly embattled with rebels making gains in northern Syria and near Damascus, the capital.

The defecting judges posted a joint statement online urging others to join them and break ranks with Assad's regime. There have been several high-level defections over the last year, including Assad's former prime minister.

In Geneva, Lakdhar Brahimi, the U.N.'s special representative for Syria and the Arab League, met with Russian Deputy Foreign Minister Mikhail Bogdanov and U.S. Deputy Secretary of State William Burns to discuss the crisis in Syria. They said in a joint statement that the situation was "bad and getting worse," adding that a political process to end the conflict was "still necessary and still possible."

Russia and the United States have argued bitterly over how to address the conflict, which began with peaceful protests against Assad in March 2011 and escalated into a civil war that has killed an estimated 40,000 people. Activists said 45 more were killed Sunday. The United States has criticized Russia for shielding the Assad regime, while Moscow has accused Washington of encouraging the rebels.

In Moscow, Russian Foreign Minister Sergey Lavrov said that Russia agreed to take part in the Geneva talks on condition there would be no demand for Assad to step down. "We are not conducting any negotiations on the fate of Assad," Lavrov said.

Addressing fears that Assad could use chemical weapons in a last-ditch effort to save his regime, Lavrov once again said the Syrian government has given assurances that it has no intention of ever using the weapons of mass destruction. He said the greatest threat is that they would fall into the hands of militants.

Russia's foreign minister said that after he agreed to a U.S. proposal to have his and Secretary of State Hillary Rodham Clinton's deputies "brainstorm" on Syria, the Americans began to suggest that Russia was softening its position. "No such thing," Lavrov said. "We have not changed our position."

In Lebanon, fighting between pro-and anti-Assad gunmen flared as bodies of three Lebanese, who were killed after crossing into Syria to fight in the civil war, were brought back home for burial, the state-run National News Agency said. Four people were killed and 12 were wounded in the gunfights, the agency said.

In Syria, fighting was concentrated in northern Idlib province, in the Damascus suburbs, and in Aleppo, according to the Britain-based opposition activist group Syrian Observatory for Human Rights. At least 45 people were killed Sunday. Syria's state-run SANA news agency said four people were killed when a rocket slammed into the Armenian quarter of the city of Homs.