U.S. Secretary of State Colin Powell has called on Venezuelan President Hugo Chavez to hold a free and fair a referendum on his presidency later this year.

In an interview Wednesday with Associated Press Television, Mr. Powell said he has "concerns" over Mr. Chavez's commitment to key democratic institutions.

But he said the referendum will be a test for Mr. Chavez to show a commitment to what Mr. Powell called "the correct form of democracy for our hemisphere."

The Organization of American States last week helped broker a deal between Venezuela's government and opposition to pave the way for holding a midterm referendum on Mr. Chavez's rule.

Mr. Chavez has noted Venezuela's constitution requires the opposition to collect 2.5 million voter signatures to hold the referendum. If approved, the vote is expected to take place after August 19.