MEXICO CITY (Reuters) - Mexican billionaire investor Carlos Slim said on Monday that his team is reevaluating a deal inked with state oil company Pemex to develop Mexico's first deepwater natural gas field, a project long plagued by problems over its commercial viability.

The comments support a Reuters exclusive last month which revealed that representatives of Slim's Grupo Carso and Pemex have discussed changes to the deal in order to make the Lakach project profitable, despite lower forecast gas prices.

"It's a complicated project that needs to be tackled by great technicians," Slim said during a press conference in Mexico City, adding that the depth at which the resource was buried in the Gulf of Mexico made it more difficult.

"It'll depend on what is being built," he said when asked repeatedly whether he was still interested in the field.

Pemex has already twice abandoned the Lakach project due to prohibitive development costs.

Slim also reiterated the need for more investment in infrastructure and that Mexico was importing the vast majority of its gas from the United States.

Reuters reported that Grupo Carso wanted to add two nearby fields with similar expected resources, Piklis and Kunah, to increase the potential profitability of the venture, and was even contemplating putting the project on ice.

In recent years, Slim has been increasing his investments in the energy sector, with stakes in shallow-water fields Zama, Ichalkil and Pokoch. Last year, his team met with Pemex officials to discuss Lakach.

Located some 90 kilometers (56 miles) from the Gulf port of Veracruz, Lakach holds an estimated 900 billion cubic feet of gas. Pressure is low at the existing well there, making production a challenge.

It needed a lot more investment, sources said, and was made more complicated by low gas prices.