By ANITA SNOW
Associated Press Writer

HAVANA -- Tens of thousands of Cubans rallied Monday, as Fidel Castro warned President Bush against launching a military attack on Cuba, saying it would provoke a mass exodus and an all-out ground war.

Washington has repeatedly denied it is planning any military action against Havana.

But an increased tightening of sanctions against the island, along with the Bush administration's pre-emptive strike on Iraq, has convinced the Cuban leadership that a military attack is not impossible.

"Do not try crazy adventures such as surgical strikes or wars of attrition using sophisticated techniques because you could lose control of the situation," Castro said in a speech addressed specifically to Bush before the morning.

"You could shatter the immigration agreement and provoke a mass exodus that we would not be in a position to prevent, and you could bring about an all-out war between young American soldiers and the Cuban people," he said. "That would be very sad."

"You would never be able to win that war," the Cuban leader said. "Here you will not find a divided people."

In May, a U.S. presidential commission delivered Bush what amounts to a policy of regime change in Cuba, recommending that the United States subvert the planned succession in Cuba under which power would pass from Castro to his younger brother, Raul.

The release of the report coincided with a new round of tough new measures that will further limit travel here by U.S. citizens -- including Cuban Americans.

Dressed in his typical olive green uniform and cap, Castro spoke at a mahogany wood podium on a stage outside the oceanfront U.S. Interests Section -- the American mission here.

The coastal Malecon highway was crowded with tens of thousands of people called out by their workplaces, schools and neighborhood authorities. The government estimated the crowd at 200,000, a number impossible to confirm independently.

The Communist Party daily Granma said the morning gathering was called to deliver Cuba's "most energetic condemnation and protest against the brutal anti-Cuban measures by the current U.S. government."

The sanctions are to take effect June 30.

The new rules by the U.S. Treasury Department's Office of Foreign Assets Control will severely limit how often Cuban-Americans can visit family and which relatives they can legally send money to on the impoverished island.

Cuban-Americans who previously could visit relatives every year will now be able to travel here once every three years.

While in the past they could send money to aunts, cousins, nephews and nieces -- along with more immediate family -- they now will be able to send financial help only to parents, grandparents, siblings, spouses, children and grandchildren.

The moves have been welcomed by more conservative Cuban exiles in Miami. But they have been rejected by other Cuban immigrants, especially those who arrived in the United States more recently and still have family on the island.

Small protests against the measures were held in Miami and Key West over the weekend.

The measures will also make it even more difficult for non-Cuban Americans to travel here legally. Students now will be prohibited from traveling to Cuba for courses that last less than 10 weeks.

This change will end a host of short educational trips sponsored here in recent years by American universities and other groups.

Copyright © 2004, The Associated Press