Felipe Calderon, the possible winner of the July 2 Mexican presidential elections, waves to photographers as he arrives for a news conference with foreign correspondents in Mexico City, Mexico on Friday.

MEXICO CITY — Leftist presidential candidate Andres Manuel Lopez Obrador urged his supporters to take to the streets Saturday, claiming the governing party stole his victory in Mexico's extremely narrow elections.

Lopez Obrador asked protesters to be peaceful during a demonstration Saturday afternoon, but warned the government would be responsible for any angry flare-ups because officials rejected his demand for a manual recount of Sunday's vote.

His conservative rival, Felipe Calderon, meanwhile, acted as if his presidential victory was secure and took a congratulatory call from President Bush on Friday.

Mexico's top election court has yet to name a president-elect because it must first weigh complaints of illegal campaign practices and certify the vote count.

Lopez Obrador, a former Mexico City mayor, has millions of devoted followers and views street protests as an effective means of pressuring the government and the courts. He claims hundreds of thousands of votes for him remain uncounted, miscounted or voided, and that a manual recount would confirm that.

"We are going to provide a channel for the great anger that exists among our supporters and those who voted for us, in the face of the manipulation of the elections," said Gerardo Fernandez, spokesman for Lopez Obrador's leftist Democratic Revolution Party.

The U.S. Embassy in Mexico City urged Americans "to avoid downtown Mexico City and surrounding areas" during the protest, noting foreigners are prohibited by law from political activity here and that "even demonstrations intended to be peaceful can turn confrontational and escalate into violence."

Calderon won by 244,000 votes, a margin of 0.6 percent, according to a final tally announced Thursday. Electoral authorities say the law allows a manual a recount only in polling places where credible evidence of irregularities exist.

Lopez Obrador's supporters say that exception applies to at least 50,000 of the approximately 130,000 polling places. But they want all the ballot boxes opened.

"Those who oppose clearing up these election results are the ones who could start to generate unrest and discontent," said Alberto Anaya, a leader of Lopez Obrador's coalition.

The parties have until Monday to file complaints with the seven-judge court, which can order investigations of the evidence, change the official results and even order new elections. The tribunal has until Sept. 6 to certify the winner, and its decision is final. The new president takes office Dec. 1.

Cheerful and confident in a meeting with foreign reporters Friday, Calderon said he would support immigration reforms in Washington and create relief programs to help Mexican farmers who will be hurt when a clause under the North American Free Trade Agreement allows for U.S. corn and bean imports in 2008.