Three US service members and a contractor have been killed by an improvised explosive device close to a major base near Afghanistan's capital, Kabul, the US military has said.
In a statement, the military said three other United States troops were wounded in the explosion and were receiving treatment.
Earlier three people were killed in twin explosions in the eastern Afghan city of Jalalabad. He said no civilians were hurt.
The Taliban claimed responsibility for the attack, adding that a suicide bomber detonated his explosives-laden vehicle near the North Atlantic Treaty Organisation base in Bagram district, in Parwan province.
Seven US service members have been killed in Afghanistan this year. The names of the casualties are being withheld for at least 24 hours pending next-of-kin notification.
Monday marked the first loss of life for U.S. forces in Afghanistan since two U.S. Army soldiers were killed late last month.
The airfield is home to thousands of USA and allied troops and contractors.
"The area is cordoned off by the coalition forces". But the Taliban say they will not recognize any government official attending the gathering as a representative of the Kabul government, only as an individual Afghan participant.
He told the House Foreign Affairs Committee on March 27 that USA officials are trying to convince all parties, including Afghanistan President Ashraf Ghani and his government, to reach a reconciliation.
Khalilzad met with Taliban negotiators most recently last month in Doha, Qatar, and both parties reported progress following the talks. He said Afghans want peace, but "they don't want to live the way that the Taliban want them to live".
"In Afghanistan, my administration is holding constructive talks with a number of Afghan groups, including the Taliban", Trump said during his State of the Union address in February.
