But Karzai stopped short of specifically asking the US to increase its 20,000-strong presence.
Speaking in Washington before a meeting with President George Bush on Tuesday, the interim president called on NATO's 6000-strong force to be increased and deployed in all provinces.
But many NATO allies say their military capability is overstretched. Some member countries are even reported to be reluctant at providing equipment such as helicopters and planes.
No specific request
The interim president was elected by a loya jirga or grand council and is now seeking a popular mandate in the elections, which were originally planned to have been held in June.
"To fulfil the promise that we have been made, we are hoping that NATO will come to Afghanistan before the elections in September."
But he did not make a specific request to the US for troops.
"The United States is already busy in Afghanistan helping us in reconstruction, and helping us fight terrorism and helping us secure our borders," he said.