Nepali King Gyanendra's decision to seize power has provoked concern from nations around the world.
The United States says it is "deeply troubled" about the apparent setback for democracy in Nepal.
A State Department spokesman said on Tuesday that King Gyanendra's actions undermine Nepal's struggle with Maoist insurgents.
In a published statement, United Nations Secretary General Kofi Annan said he is "deeply concerned" about the king's decision to dissolve the government, impose a state of emergency and suspend civil liberties.
Mr. Annan said he views the actions as a serious setback for the country.
Britain said it summoned the Nepali ambassador in London to express its concerns.
Nepal's neighbor, India, also expressed "grave concern" over the king's move, saying it would only benefit the Maoist rebels.