The United States is criticizing in strong terms the prosecution of four political opponents of Venezuelan President Hugo Chavez. The four members of the opposition group Sumate are accused of conspiracy for accepting money from a U.S. non-governmental group.

The Bush administration has had a tense relationship with Venezuelan President Chavez and it is using some of its sharpest language to date in criticizing the prosecution of the opposition figures.

A Venezuelan judge ruled Thursday that the four members of Sumate, including its leader, Maria Corina Machado, are to be tried on charges of conspiring to overthrow the government using U.S.-provided funds. A trial date has not been set.

Sumate received a $31,000 grant from the National Endowment for Democracy, the NED, a non-governmental group funded by the U.S. Congress that promotes democracy world-wide. The NED has spent more than $2 million in recent years on programs in Venezuela.

Sumate was a major force behind the unsuccessful recall referendum against Mr. Chavez last year, and its leader, Ms. Machado, had a highly-publicized meeting with President Bush at the White House in May.

At a news briefing, State Department spokesman Thomas Casey said the United States is very disappointed over the legal action against the Sumate members and said the charges against them are, in his words, without merit or foundation.

Mr. Casey said the NED funded activities Sumate was involved in were aimed at strengthening citizen participation in the democratic process, and said the criminal action is part of a broader campaign of intimidation against Chavez opponents.

"Sumate is an internationally-respected civic organization. It's committed to promoting free and fair electoral processes and respect for basic rights. And the judicial actions that are being taken here are, from our perspective, simply part of a Venezuelan government campaign that's designed to intimidate members of civil society, and prevent them from exercising their democratic rights," he said.

Mr. Casey said the United States is seriously concerned about political persecution and threats to democratic rights and institutions in Venezuela, and urges the Chavez government to honor commitments under the Inter-American Democratic Charter to guarantee all citizens' civil and political rights.

An official said U.S. diplomats would raise the Sumate case with Venezuelan officials in both Washington and Caracas.

The Venezuelan embassy here said the country's judiciary, as in the United States, functions independently of the executive branch, and that the case against the Sumate leaders is public and transparent.

In Venezuela, Ms. Machado said the criminal action was clearly an attempt to intimidate Sumate, but that the group would continue to campaign for transparency in local elections set for early next month.