John Bolton, the national security adviser of the White House, warned Venezuela not to use force against US diplomats or against Juan Guaidó who declared himself president of the country.
If that does happen, there will be an "important reaction", Bolton said.
The US and Venezuela have agreed that they will keep a leaner part of their embassies open.
The Venezuelan president Nicolás Maduro said earlier that he would break all diplomatic ties with Washington, but he partly came back to that.
Maduro watched a military exercise on Sunday, including Russian tanks and anti-aircraft weapons
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