U.S. officials say foreign powers are pulling back from their dealings with the U.S. government since hundreds of classified diplomatic cables were published on the WikiLeaks website.
State Department spokesman Philip Crowley said Washington had "already seen some indications" of this, and that it would make diplomacy "more difficult." He said the extent of the damage remains to be seen.
"We do recognize that on a country-by-country basis there could well be some impacts. We've already seen some indications of meetings that used to involve several diplomats that now involve fewer diplomats," Crowley said.
"I think we're conscious of at least one meeting where it was requested that notebooks be left outside the room."
The data dump by WikiLeaks includes detailed exchanges between foreign and U.S. officials on politically sensitive matters.
Earlier, U.S. officials condemned WikiLeaks for releasing a secret list of sites around the world that Washington considers critical to its national security.
Secretary of State Hillary Clinton said the list had been stolen from the U.S. government.
The list includes sites such as mines, companies involved in weapons systems, producers of vaccines and medicines, undersea communications cables, and energy routes in locations around the world.
U.S. Attorney General Eric Holder said work was continuing toward the possible prosecution of those behind the release of the information.
compiled from agency reports