The US ambassador to Afghanistan, Ryan Crocker, announced Tuesday he would be leaving Kabul in mid-summer for health reasons, dpa reported. His departure will follow the Kabul and Tokyo conferences on Afghanistan, the US State Department said. "Ambassador Crocker's tenure has been marked by enormous achievements," spokeswoman Victoria Nuland said. Crocker played a key role in negotiating the US-Afghan strategic partnership agreement that charts the US role in Afghanistan after foreign troops withdraw in 2014. He has been ambassador in Kabul since 2009. Before that, he served as ambassador to Iraq, Pakistan and Syria, where he first served in 1998.