By THE ASSOCIATED PRESS

Filed at 8:50 p.m. ET

The signature campaign, running from Saturday morning through noon Tuesday, is being carried out at more than 120,000 stations around the country.

By the end of Saturday, 69.6 percent of Cubans age 16 or older had signed, ``passing all'' forecasts, Pedro Ross Leal, head of the Confederation of Cuban Workers, told state radio stations Sunday. The legal voting age here is 16.

Fidel Castro was the first to sign on Saturday and estimated that at least 7 million of Cuba's 11 million citizens would follow in support of the petition for a constitutional amendment declaring the nation's economic, political and social system cannot be changed. That figure roughly matches the number of people of voting age.

Opposition activists say the petition drive is Castro's answer to their own civil liberties campaign, known as the Varela Project. Most Cubans first heard of the Varela Project last month in a speech by former President Carter when he visited the island.

Government officials expect most Cubans to sign, but a number of dissidents complained that no political or economic system should be engraved in stone for future generations and questioned whether Cubans were signing of their own free will.

The mass organizations running the signature campaign -- including the Committees for the Defense of the Revolution that watch every block in each neighborhood, the Federation of Cuban Women and the Confederation of Cuban Workers -- officially are autonomous. But all play key roles in supporting and protecting the socialist system.

Castro, 75, has insisted repeated that Cuba will remain socialist after his death. His designated successor is his brother, 71-year-old Defense Minister Raul Castro.

Opposition activists mounted the Varela Project seeking a referendum to ask voters whether they favor such civil liberties such as freedom of speech and assembly, the right to own a business, electoral reform and amnesty for political prisoners.