The United States has frozen the assets of the Maoist Communist Party of Nepal and issued a new warning to American citizens in the country.
The Maoists have given conflicting signals on targeting Americans
A statement issued in Washington by the State Department listed the party as a threat to US national security.
The US embassy in Kathmandu warned its citizens in Nepal of an "increased threat from Maoist insurgents in the coming days".
Nearly 8,000 people have died since the Maoists began fighting to replace the government in Nepal in 1996.
The embassy did not give details of specific dangers but urged Americans and US-affiliated organisations to keep a low profile and exercise caution.
Last week, Maoist leader Prachanda said the group was changing its strategy to target US-backed organisations and would halt attacks on government infrastructure.
However on Monday, the Maoists said Americans not helping Nepal's army would be safe.
Nearly 8,000 people have died in the insurgency since 1996
In Friday's State Department document, US Deputy Secretary of State Richard Armitage said: "The Communist Party of Nepal... has committed, or poses a
significant risk of committing, acts of terrorism that threaten the security of US nationals or the national security, foreign policy or economy of the United States."
The document also proscribed two of the party's aliases - the United Revolutionary
People's Council and the People's Liberation Army of Nepal.
Washington holds the Maoists responsible for the deaths of two embassy
guards in 2002.
It is not known whether the party has any assets under US jurisdiction that can be frozen.
The Maoists ended a seven-month ceasefire in August and more than 1,000 people have died since then in renewed clashes.