The summit is also a chance to smooth regional differences

The ministers, in Uruguay for the 16th Ibero-American summit which runs until Sunday, said the fence would promote discrimination and xenophobia.

Their draft declaration still needs to be approved by leaders.

Last month, President Bush signed into law plans for fencing on the US-Mexico border, to curb illegal immigration.

About 10 million Mexicans are thought to live in the US, some four million of them illegally.

Mexico argues the fence will do little to ease illegal entries and will likely increase deaths along the border.

A draft of a final declaration by the leaders of Spain, Portugal and Latin America gathering includes a special statement rejecting the fence plan.

"We express our deep concern over the decision adopted by the government of the United States," the draft says, adding that regional leaders want to call on the US to reconsider its decision.

Absentees

The main aim of the Ibero-American summits is to bring the Spanish and Portuguese-speaking world together - to tackle common problems and to share in their joint successes.

They can also be pressure points for long-running regional and international disputes.

Among those attending are King Juan Carlos of Spain, the outgoing United Nations Secretary General Kofi Annan and Bolivia's President Evo Morales.

But the opening ceremony was marked as much by who was not there as who was, says the BBC's Daniel Schweimler in the Uruguayan capital, Montevideo.

Cuban leader Fidel Castro is still recovering from surgery, Luiz Inacio Lula da Silva is resting after being re-elected as president of Brazil, while Hugo Chavez of Venezuela and Peru's Alan Garcia sent their apologies.

When those who did make it get down to business, they will be discussing migration, our correspondent says.

Millions leave the region every year to seek a better life in the US and Spain, some facing discrimination and exploitation but also sending millions of dollars in vital remittances back to their home countries.

The summit is also an opportunity for protesters, opponents of free trade deals and environmentalists among others, to express their opinions.