Cuban President Fidel Castro has condemned new moves to tighten the US embargo on the island from next month.
Castro warned Bush against "crazy adventures"
Mr Castro told a rally of more than 200,000 people in Havana that the new US rules were "merciless and inhumane".
He accused Washington of planning an attack on Cuba, saying the move could spark a mass exodus from the island.
The new measures, which were published on 6 May, include tighter curbs on money sent home by expatriate Cubans living in the US.
The White House says it wants to limit the flow of dollars to Cuba, which it believes are being used to maintain Mr Castro's communist administration.
The new rules also tighten restrictions on travelling to Cuba and increase financial support for dissident groups.
"Our people will stand up to your economic measures,
whatever they may be," Mr Castro told the cheering, flag-waving crowd.
"Forty-five years of heroic struggle against the blockade have not weakened but strengthened the revolution," he said.
In remarks aimed specifically at US President George W Bush, the Cuban leader said: "Do not try crazy adventures, such as surgical strikes or wars of attrition using sophisticated techniques, because you could lose control of the situation."
Correspondents say Washington has repeatedly denied that it plans military action against Cuba, but the leadership in Havana is convinced that an attack is not impossible.
Under the new US measures, which take effect on June 30:
- Family visits by Cuban-Americans will be limited to once every three years instead of the current one per year
- Dollar transfers that Cuban-American families can send to the island will still be limited to $1,200 a year
- Remittances and gift parcels will be limited to
immediate family members - recipients may not include "certain Cuban officials and Communist Party members"
- The authorised daily amount for a family visit will be lowered from $164 to $50.