MEXICO CITY (Reuters) - Mexico’s presidential frontrunner Andres Manuel Lopez Obrador should decide quickly on whether to scrap a new Mexico City airport if he wins the July 1 election, a top adviser said on Friday.

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The leftist candidate, who has led opinion polls for months, has threatened to scrap the $13 billion project on the eastern flank of the city, arguing it is tainted by corruption and will be too expensive due to its technical and geological complexities.

Javier Jimenez Espriu, Lopez Obrador’s pick to head the transport and communications ministry, said the airport, which is being built on the bed of the former Lake Texcoco, must be subject to a thorough audit to asses its viability.

“It needs to be very quick,” Jimenez said in an interview in Mexico City. “I would say that we decide it in two months. That would be my position as of today.”

Jimenez said Lopez Obrador would seek to halt work on the airport almost immediately if he is elected in July. However, the new president would not take office until December.

By then, the airport would be 40-45 percent complete, according to Grupo Aeroportuario de la Ciudad de Mexico (GACM), the company in charge of completing the project. Canceling it would cost about 120 billion pesos ($6.5 billion)and destroy thousands of jobs, the company said.

As an alternative new airport, Lopez Obrador has proposed repurposing and extending a military air base to the north of the capital and keeping the current airport, which has been straining at its capacity limits for years.

However, the government of President Enrique Pena Nieto has said the two could not operate simultaneously and that the new airport, which would more than double the capacity of the current hub, is the best option.

The threats to scrap the project by Lopez Obrador, a former Mexico City mayor, have rattled business leaders and sparked a standoff between him and the country’s richest man Carlos Slim. Slim has a major stake in the construction of the hub.

The terminal building of the airport was designed by British architect Norman Foster and Slim’s son-in-law, and firms owned by the Mexican tycoon are involved in the construction.

Earlier this month, Slim said the new airport should have been contracted as a concession, but Jimenez said he did not believe that was appropriate for such a strategic project.

($1 = 18.6085 Mexican pesos)