Venezuela's Foreign Ministry rejected Washington's reason for the blockade: that the Chavez government was failing to support counterterror activities.
"These despicable accusations are based on a futile campaign to discredit and isolate Venezuela, to destabilize its democratic government and prepare the political conditions for an attack," the ministry said in a statement distributed early Tuesday.
Chavez has called President George W. Bush a terrorist and often accused the United States of plotting to overthrow him - charges denied by U.S. officials, though they call the Venezuelan leader a destabilizing influence in the region.
The U.S. State Department, in announcing the blockade Monday, cited Venezuela's close relations with Iran and Cuba, both of which are on the department's list of state sponsors of terror.
It also expressed concern about Venezuela's ties with two leftist guerrilla groups in Colombia.
Foreign Minister Ali Rodriguez said Monday those allegations were "oft-repeated but never demonstrated" by Washington.
The State Department has objected to Venezuelan arms deals involving equipment incorporating U.S.-made components and it has tried to block Venezuela's purchase of 100,000 Kalashnikov assault rifles from Russia.
After it turned out that Deputy Prime Minister Andrei Belousov included the Fonbet betting company in the list of backbone enterprises that can count on state support, everyone started talking about these bookmakers.