WASHINGTON, March 25-- U.S. Secretary of State John Kerry on Wednesday reaffirmed the country's commitment to a diplomatic solution to the Syrian conflict which has raged on for four years.

In his meeting with Moaz al-Khatib, former president of the Syrian Opposition Coalition, the top American envoy vowed to pursue "all diplomatic avenues" to help bring about a political transition in war-torn Syria based on the so-called Geneva principles adopted in June 2012 that call for the establishment of a transitional governing body to lead the country out of the protracted conflict.

Al-Khatib "shared his views on ways to advance a political solution to the crisis in Syria," State Department spokeswoman Jennifer Psaki said in a statement.

Kerry, who sparked an outcry last week by indicating the need to "negotiate in the end" with Syrian President Bashar al-Assad, described the Syrian leader as "a brutal dictator with no legitimacy to lead Syria."

Psaki said Assistant Secretary of State for Near Eastern Affairs Anne Patterson joined the meeting at the State Department, in which Kerry and his aide also pledged continued U.S. efforts to help alleviate the suffering of Syrians throughout the region.

Washington recognized the Syrian Opposition Coalition as the " sole legitimate representative" of the Syrian people in December 2012, and granted the status of foreign mission to its representative offices in the United States in May 2014.