Cuba's foreign minister opened a summit of more than 100 of the world's developing nations Monday, saying the Nonaligned Movement is more needed than ever in such an "unjust world."

Felipe Perez Roque said current global and political problems highlight the need for unity in the movement, originally developed during the Cold War and fighting for relevance in the 21st century.

"Today we can affirm ... that the movement is more necessary than ever," Perez Roque said in Havana.

Some 50 heads of state and U.N. Secretary-General Kofi Annan are expected to attend the summit by week's end. Cuba will take the chairmanship of the movement from Malaysia, which Perez Roque praised for its work in the last three years.

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It's unclear what role Cuba's ailing leader Fidel Castro will play, if any, in hosting the leaders of countries from Africa, Asia, the Middle East and Latin America.

Perez Roque said Sunday he could not confirm whether Castro will host a Friday dinner for visiting leaders as noted in a schedule released earlier in the day, raising new doubts over Castro's participation. If Castro does make the dinner, it would be his first public appearance since he underwent intestinal surgery more than a month ago.

Formed in 1961, the Nonaligned Movement was originally comprised of nations trying to form a Third-World force through a policy of nonalignment with the United States or the Soviet Union.

But heading into the meeting, Cuban officials have said the movement is still relevant despite the end of the Cold War, with smaller, developing countries needing to band together to resist the intervention and aggressions of more powerful nations.

Among well-known leaders attending are Presidents Mahmoud Ahmadinejad of Iran, Pervez Musharraf of Pakistan, Bashar Assad of Syria and Thabo Mbeki of South Africa, as well as Prime Ministers Manmohan Singh of India and Thaksin Shinawatra of Thailand.

Castro has long been a major player in the movement, and a schedule sent to international media Sunday morning listing him as hosting a dinner for visiting dignitaries, seemed to end speculation over whether he will make any appearance at this week's gathering.

But Perez Roque's refusal to confirm that, and his subsequent comments, cast new doubts about Castro would participate.

"Fidel is recovering satisfactorily, the worst has been left behind," Perez Roque told a news conference.

"I cannot yet confirm his presence at the dinner," Perez Roque said. "I can confirm that the head of the Cuban delegation at that moment will be offering those dignitaries that dinner.

"If Fidel is not there, then Raul will act as host at the dinner," the foreign minister added, referring to the 80-year-old leader's brother, Defense Minister Raul Castro, 75, who is acting as Cuba's provisional leader.

"Logically, the physical absence of Fidel in all of the summit work constitutes a notable loss," Perez Roque said. "All of us would like him to head the delegation and be there all the time. If that does not occur, we have made great preparations under his personal direction."

After the news conference, a different version of the Nonaligned schedule was sent to international journalists permanently accredited in Cuba, with a note saying it was the "valid" version. Although the Friday night dinner was still listed, any mention of Castro hosting it had been removed.

Fidel Castro announced July 31 he had undergone emergency surgery for an undisclosed intestinal ailment and provisionally handed over power as Cuba's president and Communist Party head to his brother Raul.

The nature of Castro's surgery and his specific ailment have been treated as a state secret, although photographs and statements from him have been released.

Earlier in the week, Castro said in a statement published in state media he would be able to meet with some visiting dignitaries, but gave the sense that those meetings would be small and private.

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