The future of Mexico City's new airport, already about a third completed, comes down to a public vote this week in a political high-wire act by the country's president-elect that could shut down Mexico's largest infrastructure project in recent memory.

President-elect Andres Manuel Lopez Obrador promised to let the people decide the fate of the USD 13 billion airport designed in collaboration with celebrated architect Norman Foster.

Lopez Obrador had earlier said he would cancel it if elected, his victory being a referendum in itself.

Over four days beginning Thursday, citizens will cast ballots asking whether to continue with the new airport or update Mexico City's existing one and another airport two hours away in Toluca, while building two new runways at a military base that would be converted to commercial use.

Supporters of the new airport say it is needed because Mexico City's Benito Juarez International Airport handles more traffic than its designed capacity and a solution is urgently needed to satisfy growing demand.

Surrounded by densely packed residential neighbourhoods, the old airport has no room to add new runways.

And supporters point to a study by US corporation Mitre showing that while the alternative plan is technically feasible, it presents important logistical problems and overall is unviable.

Opponents counter that not only is the new airport a potential sinkhole of corruption, but it would be an environmental disaster, threatening a decades-old effort to restore the lakes that originally covered the valley in which the capital is located. Locals also claim they were not consulted about the project.

Lopez Obrador has said he wants to remain impartial, but he and his Cabinet picks consistently make the case against the new airport, characterising it as too expensive and a windfall for corrupt interests.

Last week, he said the second option could save USD 5 billion. He hasn't said, though, what will be done with the skeletal remains of new airport if it loses.

About USD 6 billion has already been poured into the site northeast of Mexico City.

"Corruption is over, influence is over, impunity is over," Lopez Obrador said in a recorded message this month.

"We're going to resolve this issue in the way that best suits Mexico, the national interest, and what the people decide."

Ivonne Acuna Murillo, a professor in the political science department at Iberoamericana University in Mexico City, said Lopez Obrador has continually said he wants to govern with and for the people.

He won 53 percent of the votes in July's election and takes office December 1.

"He understands very well where his strength lies," she said.

Still, Acuna believes Lopez Obrador is playing a bit of a "cat and mouse" game trying to pressure Mexico's business elite into footing the bill for the airport.

It could be working. On Tuesday, current tourism minister, Enrique de la Madrid, said on a local radio show the new airport is such a good business that it could be paid for without public funds.

On a recent morning, Lopez Obrador's pick for transportation minister stood above an open pit mine where trucks were dumping loads of muddy sediment from the new airport site about 10 miles (16 kilometers) away.

Wearing a cream-coloured cowboy hat and surrounded by residents of communities near the new airport, Javier Jimenez Espriu said he was gathering information and helping to inform citizens about the project and its impact.

His talk was interrupted by Felipe Alvarez Hernandez, a member of Peoples in Defense of the Earth Front, a group that has been fighting proposed airports in the area for nearly two decades.

"If the (vote) is going to say that it should continue, then you are violating our rights with the query," Alvarez said, holding his machete aloft.

Jimenez asked the crowd what they wanted.

"That it's cancelled, that's all," Alvarez said.

A previous attempt to build a replacement Mexico City airport in San Salvador Atenco in 2002 was cancelled due to local opposition.