backed investigation in Lebanon over the killing of former prime minister Rafiq Al-Hariri has soured a tentative rapprochement between the United States and Syria. The two countries exchanged tough rhetoric over the last two weeks, with President Bashar Al-Assad accusing the United States of spreading chaos in the world and US officials accusing Syria of trying to undermine stability in Lebanon. The war of words underlined how little progress President Barack Obama's engagement policy with Damascus has yielded. The bitter words are unlikely to derail the relationship completely because both countries need each other to advance their strategic goals. But neither Syria, which seeks US pressure on Israel to end its four-decade occupation of the Golan Heights, and Washington, which wants Damascus to curb its ties with Iran and Islamist groups, feels the other has delivered tangible results. “Both sides have been sitting on the fence. Syria is disappointed with the Obama administration,” one Western diplomat in Damascus said of Obama's efforts to engage with Syria since he took office in January last year. The United States named a new ambassador, Robert Ford, to Damascus in February, nearly five years after withdrawing its envoy following the assassination in Beirut of Lebanese statesman Rafiq Al-Hariri – a killing which Syria's foes in Lebanon blamed on Damascus. Syria has denied any involvement. But Congress has yet to approve Ford's appointment, and Syria has shown no sign of addressing US hopes it will cut support for Lebanon's armed Shiite group Hezbollah and the Palestinian Islamist Hamas, or distance itself from Iran. “Syria and the United States have been keeping the engagement process on life support; that's all that's been happening for the last year,” said Peter Harling of the International Crisis Group. US Senator John Kerry, speaking in Beirut on Monday, expressed regret that domestic “partisan politics” were holding up Ford's assignment. But he said progress on that front would also depend on Syrian behavior. “So we will look to Syria to play a constructive role in these next days in what happens here in Lebanon,” he said. Assad told the pan-Arab newspaper Al-Hayat in an interview published last month that the United States had “created chaos in every place it entered”, pointing to interventions in Afghanistan, Somalia and Lebanon. A Western diplomat in Damascus said the barbed comments surprised US officials after what he described as a positive reception in Syria for US Middle East envoy George Mitchell, who is trying to revive Israeli-Palestinian peace talks. Two days after Assad's remarks, the US ambassador to the United Nations, Susan Rice, accused Damascus of displaying “flagrant disregard for the sovereignty, territorial integrity, unity and political independence of Lebanon”. Western diplomats say the outburst reflects growing US concern that Syria, which still wields influence in Lebanon five years after it withdrew its troops, has stepped up efforts to obstruct the UN-backed investigation into Hariri's killing.