Robert Ford, the US ambassador to Syria who has been Washington's main pointman in efforts to end the war working with opposition leaders battling President Bashar al-Assad, stepped down Friday.
"Robert Ford is retiring from the foreign service today after nearly 30 years of distinguished service," State Department spokeswoman Jen Psaki told reporters.
She admitted that the departure of Ford, who over the past three years has built up extensive contacts with the opposition leaders and was instrumental in helping to bring them to the Geneva peace talks, would be a loss.
"His extraordinary leadership has guided our response to one of the most formidable foreign policy challenges in the region," Psaki said.
"From the outbreak of the crisis, Ambassador Ford has worked tirelessly in support of the Syrian people in their pursuit of freedom and dignity."
A fluent Arabic speaker, Ford became Washington's first ambassador to Damascus in five years when he was named in late 2010.
But just a few months into his post, Ford was abruptly pulled out of the country in October 2011 amid fears for his safety when he became a vocal critic of the Assad regime and its crackdown on the pro-democracy uprising that erupted in March that year. He never returned full-time to Syria.
Ford was increasingly criticized by the regime, which accused him of helping incite violence and was angered when he visited protest hubs outside the capital in a show of solidarity with pro-democracy demonstrators.
In late September 2011, Ford was blocked inside a building for a few hours during a meeting with opposition member Hassan Abdel Azim when nearly 100 angry pro-regime protesters tried to storm the offices.
Washington decided to close the embassy in 2012 as the uprising descended swiftly into a bloody civil war.
Since then, Ford has shuttled between the United States and Turkey, spending hours huddled with opposition leaders based out of Istanbul as he sought to help them form a more cohesive and inclusive body.
Ford has also spoken passionately and angrily about the mounting atrocities in the war, which will enter its fourth year next month and in which more than 136,000 people have been killed and millions displaced.
A career foreign service officer, Ford also served as deputy chief of mission in Baghdad from 2008-2009. He was ambassador to Algeria from 2006 to 2008 and had postings in Bahrain, Cairo and Yaounde.
But he often spoke of his love for Syria, its culture, heritage and people.
"There's no question that his departure is a loss, not just because of his contacts, but because of his expertise, because of his knowledge," Psaki said.
She announced that for the time being, as the White House mulls a replacement for Ford, Acting Deputy Assistant Secretary Lawrence Silverman would take up the helm.
"There will be a continuity, given that there (is) a range of officials who will still be in place," Psaki said.
"Obviously, part of what I'm sure will be looked at is the role that the next person will play in terms of their engagement with the opposition."
The UN-led Geneva II peace talks broke down on February 15 and no new date has yet been set for them to reconvene.
But Psaki insisted that as the United States seeks to prepare for "a new Syria," Ford's "legacy will guide our efforts to support Syrians and lay the foundation for a more hopeful future."
"The president and the secretary (John Kerry) of course are both incredibly grateful for his service."