http://news.bbc.co.uk/2/hi/americas/4092647.stmCuba's armed forces have begun their biggest military exercise for nearly 20 years, involving hundreds of thousands of troops and civilians.
The exercise, called Bastion 2004, is a response to "the continued aggression and threats" of the US, Cuba says.
The manoeuvres are being led by Defence Minister Raul Castro - brother to Cuban President Fidel Castro and second in the Cuban hierarchy.
The drills highlight current Cuba-US tensions, correspondents say.
The exercise will involve exercises with Cuban air force MiG-29s, anti-aircraft units and elite troops.
Two days of civil defence exercises at the end of the week-long exercise will include a simulated aerial assault.
The exercise involve about 100,000 soldiers, some 400,000 reservists, and "millions" of civilians, according to the Cuban authorities.
Many Cuban civilians already belong to the thousands of neighbourhood Committees for the Defence of the Revolution, whose duties include maintaining readiness against attack.
"The determination of the US administration to destroy the [Cuban] revolution however they can, including militarily, determines the necessity of conducting these exercises," said General Leonardo Andollo, deputy chief of the armed forces, according to AFP news agency.
Last week, the defence minister said the exercises would ensure "the enemy does not underestimate" the Cuban people.
The US sponsored a failed attempt by Cuban exiles to invade Cuba at the Bay of Pigs in 1961 but US officials are scornful at the idea another attempt would be mounted.
'Imaginary'
"The Cuban regime is the real threat to the Cuban people, not an imaginary US invasion," one official told the Miami Herald newspaper on condition of anonymity.
"Castro's playing the victim isn't convincing anyone. What the regime is really afraid of is the free flow of ideas, open political discourse and the Cuban people's wanting a better life and the right to select their own leaders," the official said.
The US and Washington have exchanged a series of blows over the past year, with the US tightening its tough sanctions on the island and Cuba retaliating by imposing a tax on the use of US dollars.
Venezuelan President Hugo Chavez was expected to arrive in Havana on a two-day visit on Monday, reports said - his second visit in just over one month. There were few details on his itinerary.