The attack came as visiting U.S. Defense Secretary Robert Gates planned to meet with President Hamid Karzai and other Afghan officials in the capital, Kabul .
Gates was "nowhere near the blast," said a U.S. Embassy official who spoke on condition of anonymity because she was not authorized to speak on the issue publicly.
The bomber struck a two-vehicle convoy belonging to NATO's International Security Assistance Force near the city's airport, Interior Ministry spokesman Zemeri Bashary said.
Twenty-two civilians were wounded in the attack, NATO said in a statement.
There were no casualties in the NATO convoy, said Lt. Col. Thomas Dillschneider, an ISAF spokesman.
The attacker's car was completely destroyed and three private vehicles, including a minibus, were damaged, said an Associated Press reporter at the scene.
Ten people who were riding in the minibus near the blast were among those wounded, said Ghulam Rasool, a police officer.
Militants have launched more than 130 suicide attacks this year - a record number. At least 6,200 people have died in insurgency-related violence in 2007, also a record, according to an Associated Press tally of figures from Afghan and Western officials.
Suicide attacks frequently target international and Afghan security forces, but most of the casualties are civilian passers-by.
On Monday, another suicide bomber blew himself up next to a police patrol in southwestern Nimroz province, killing two police officers and two civilians, said provincial Governor Ghulam Dastagir.
The blast also wounded three officers and four civilians, Dastagir said.
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