Second attack this week underscores Afghan government warnings that a preliminary US-Taliban deal on ending the war is moving dangerously quickly

Tractor rigged with explosives rips through residential area near compound housing international organizations

Trump hopes to bring back thousands of troops before the 2020 election

President Ashraf Ghani says Taliban also to blame for violence ravaging country, calls on people of Pakistan to help rout out safe havens for fighters in their country

No immediately claim of responsibility for attack, in which 15 are wounded, most in critical condition