SANA'A: Yemen's embattled president Tuesday warned that a coup attempt could spark civil war. The warning came as pressure mounted on President Ali Abdullah Saleh to step down and two soldiers were reported killed in a clash between rival units. With tanks deployed on the streets of the capital, Saleh warned in an address to his top brass: “Any attempt to reach power via a coup will lead to a civil war in the country.” In the same breath, the president pledged to step down by year's end. Commenting on the current instability, US Defense Secretary Robert Gates said it could distract attention from Yemen's fight against Al-Qaeda. Saleh has since faced mass protests across Yemen since January calling for his ouster. He also said at the meeting broadcast on state television that “any division in the armed forces will have a negative impact on the whole country.” Medics and witnesses said two soldiers died in a clash between the regular army and the Republican Guard, an elite force loyal to Saleh, in the southeastern city of Mukallah. The two forces clashed near a presidential palace in Mukallah late Monday, witnesses said. “The bodies of two soldiers, one of a soldier with the army and another of a member of the Republican Guard, were brought in” to a hospital in Mukallah, the medics said. Saleh's son Ahmed commands the Republican Guard, while other family members head other elite units. On the army side, Gen. Ali Mohsen Al-Ahmar, who commands the northwest region covering Sana'a, eastern region commander Gen. Mohammed Ali Mohsen, and other officers Monday pledged support for the protesters. The defections continued Tuesday, as one after another, soldiers and officials announced their support for the “youth revolution” at the square near Sana'a University where protesters have kept vigil since Feb. 21. A slew of ambassadors and other officials have either resigned or pledged their support for protesters since last week, while leading Muslim clerics have called for Saleh to “respect the will of the people” and step down. Ambassadors to Pakistan, Qatar, Oman and Spain as well as the Yemeni consul in Dubai have decided to back anti-regime protesters, Gulf News daily reported. US Defense Secretary, who is in Moscow, said “we are obviously concerned about instability in Yemen. “Instability and diversion of attention from dealing with AQAP (Al-Qaeda in the Arabian Peninsula) is certainly my primary concern about the situation,” he said in reference to the network's branch in Yemen. In addition to the latest political crisis, Saleh's government is faced not only by a challenge from AQAP, but also by Shiite rebels in the north and separatist elements in the south. Despite the defections, Saleh, in power since 1978, has said the “majority of the people” were still with him, while “officers and diplomats (who have defected) are falling to the ground like autumn leaves.” “It is not too late for them to return to reason,” he said.