"Powell provided an overview of current US government assistance to Nepal designed to help create a more prosperous, democratic and stable Nepal," the embassy said.
Dahal, who goes by the name of Prachanda or the "fierce one," led the Maoists to a surprise victory in the April 10 elections, winning more than one third of seats in the assembly.
The Maoists, who launched a civil war in 1996, were placed on a list of "terrorist organisations" by Washington in 2003 and are yet to be removed.
|"Any decision to alter that designation ... depends on the Maoists' actions, including a rejection of violence to achieve political goals"|
US embassy spokesman
During the landmark elections, Jimmy Carter, the former US president, whose Carter Centre was monitoring the polls, urged the US government to take the group off the list.
However, the US embassy said that it was likely to be some time before they would be removed.
"We at the embassy are working with government colleagues in Washington to review the current designation of the Maoists on the Terrorist Exclusion List, and Specially Designated National List," an embassy spokesman said.
"Any decision to alter that designation would take some time, it depends on the Maoists' actions, including a rejection of violence to achieve political goals," the spokesman said.
The Maoists, who won 220 of the 601 seats in the assembly, have said they plan to lead the government with or without the parties they defeated.
Last month's polls were a key component of a 2006 peace deal reached between the leftists and mainstream parties.
Nepal's King Gyanendra looks almost certain to be the last in a 240-year line after the Maoists asked him to step down gracefully before his dynasty is officially abolished.