Feltman, who has led talks with Damascus on U.S. engagement with Syrian President Bashar Assad, was slated for assistant secretary of state for Near Eastern affairs.
Levin held up Feltman's nomination over disputes stemming from settlements for Michigan residents related to Libyan-sponsored attacks, including the downing of Pan Am Flight 103 over Lockerbie, Scotland, in 1988.
Sources to The Detroit News said the issue is over compensation for a Michigan resident who was not a U.S. citizen at the time of the attacks.
Feltman had led several high-level trips to meet with the Syrian president to discuss engagement with the Baathist regime in Damascus.
Assad met Thursday with U.S. officials in Damascus, praising U.S. President Barack Obama for his stance on Syria, the official Syrian Arab News Agency reports.
The visit by U.S. officials to Damascus is the sixth since Obama assumed office in January.
Meanwhile, in unscripted comments before the Foreign Policy Association, a New York think tank, Levin, a Democrat, lashed out at former U.S. Vice President Dick Cheney for his conduct related to harsh interrogation techniques.
"If the abusive interrogation techniques he champions -- the face of which are the pictures of abuse at Abu Ghraib (prison in Iraq) -- if they are once more seen as the face of America our security will be severely set back," Levin said.
Levin is chairman of the Senate Armed Services Committee.