The United States Friday called on the government of Azerbaijan to ensure a "free and fair" presidential election October 15, though it declined substantive comment on the likelihood that ailing President Heydar Aliyev will be succeeded by his son.

The United States has renewed its call on authorities in Azerbaijan to allow a free election, following the announcement late Thursday that President Aliyev was dropping out of the campaign in favor of his son, the recently-named Prime Minister Ilham Aliyev.

The elder Mr. Aliyev, who is hospitalized in the United States with heart trouble, revealed the decision in a statement read on local television saying he was retiring for health reasons and endorsing the candidacy of his son, whom he described as his political successor.

The action had long been predicted by opposition politicians in Azerbaijan, who condemned the move as an attempt to impose a "hereditary monarchy" on the Central Asian country.

At a news briefing here, State Department spokesman Richard Boucher said the retirement of President Aliyev is an internal matter for Azerbaijan while stressing the U.S. interest in a fair election process. "The withdrawal of President Aliyev is an internal matter for Azerbaijan. The United States government has worked closely with President Aliyev in the past. We have been a good friend of Azerbaijan. We look forward to free and fair presidential elections on October 15. It's very important to us that these elections meet the standards of the Organization for Security and Cooperation in Europe, and we've long made that clear and worked toward that end," Mr. Boucher said.

President Aliyev appointed his son prime minister two months ago under terms of a new constitution approved last year in a referendum criticized by the United States and other countries as having been, among other things, hastily-arranged.

The parliament in Baku overwhelmingly approved the nomination of Ilham Aliyev, a 41-year-old former state oil executive, and the State Department said in August his appointment was "fully consistent" with the constitution.

However, U.S. spokesmen have since expressed concern about the conduct of the presidential campaign, including the denial of candidate registrations, arrests of political activists and harassment of opposition candidates.

Mr. Boucher said the United States has provided more than $2 million in aid this year aimed at supporting a democratic election process in Azerbaijan.