Mexico City ? As Mexico launched the official recount of presidential vote tallies Wednesday, conservative Felipe Calderon insisted his slim lead from a preliminary count would hold, and he said he would be willing to include his leftist rival in his Cabinet as a show of unity.

“Mexico needs us all,” Calderon said in an exclusive interview with The Associated Press.

In spite of Calderon’s confidence, the recount as of late Wednesday showed the former Mexico City Mayor Andres Manuel Lopez Obrador with a slight lead. It was considered far from certain that the trend would hold.

Insisting he was victorious, Lopez Obrador threatened to ignore the final tally because of “serious evidence of fraud.”

Election workers at 300 district headquarters across the country were adding up the tallies compiled election day by poll volunteers. Under law, they must work around the clock. With 80 percent of the tally sheets recounted, Lopez Obrador had 37 percent, compared with 35 percent for Calderon.

The preliminary count completed earlier in the week had Calderon winning by 1 percentage point. Leonel Cota, president of Lopez Obrador’s party, accused election officials of deliberately mishandling that count to confirm a win for Calderon, the ruling-party candidate. He said Lopez Obrador won Sunday’s vote.

“We are not going to recognize an election that showed serious evidence of fraud, that was dirty from the start, manipulated from the start,” he said.

A Mexican soldier keeps inventory of the ballot boxes that leave a secure area for the final count of the presidential election in Mexico City. The official recount began Wednesday.

When polls closed, citizens staffing the 130,488 polling places opened the ballot boxes and counted the votes, then sealed them into packages with their tallies attached and reported unofficial totals to the Federal Electoral Institute, or IFE. The institute then posted preliminary results on its Web site from about 41 million ballots cast.

The sealed packages were delivered to district headquarters, where elections workers used the tallies Wednesday to add up the formal, legal vote totals.

Workers were not reviewing individual ballots except when the packages appeared tampered with or their tallies were missing, illegible or inconsistent – including at least 2.6 million ballots likely to shrink Calderon’s lead to 0.64 percent if included, election officials said Tuesday.

At one electoral office in Mexico City, officials opened a ballot box because the vote tally was missing. The votes were then recounted out loud while 10 party representatives stood by with tape recorders and video cameras.

“I’m exhausted. I’m still tired from election day,” said counter Rocio Sanchez, 41, an IFE employee. “But this is something we have to do by law.”