(Reuters) - Billionaire Carlos Slim is looking to sell a minority stake in Telesites SAB de CV SITESB1.MX, the Mexican wireless tower company that he controls, people familiar with the matter said on Friday.

Mexican billionaire Carlos Slim attends a conference of the Circulo de Montevideo Foundation and Former President's Summit in Buenos Aires, Argentina May 11, 2017. REUTERS/Marcos Brindicci

The move comes 18 months after sweeping regulatory reforms forced Slim to spin off Telesites from telecommunications company America Movil SAB de CV AMXL.MX. Telesites shares have risen only slightly since then, as the company struggles to diversify beyond America Movil as its main client.

Slim and family members own about 61 percent of the shares, according to Telesites’ annual report.

Slim is speaking to private equity firms, sovereign wealth funds and infrastructure funds about selling the stake without giving up control of Telesites, the people said this week.

The sources requested anonymity because the talks are confidential and cautioned that a deal was not certain.

Telesites declined to comment. A representative for Slim, whose net worth is pegged by Forbes at $65 billion, also declined to comment.

Since its spin-off in December 2015, Telesites has been unable to attract many tenants to the towers besides America Movil and its mobile unit, Telcel. It competes with American Tower Corporation AMT.N in Mexico.

“We see little progress in third-party usage of Telesites’ towers,” Itau BBA analyst Gregorio Tomassi said in a May 3 research note. It noted that AT&T, another wireless player in Mexico, has not increased its demand for Telesites towers.

Private equity firms have traditionally invested in tower companies for their steady cash flows. Buyout firm KKR & Co LP KKR.N bought a 40 percent stake in Spain's Telefonica SA's TEF.MC tower subsidiary Telxius earlier this year for 1.275 billion euros.

Telesites has a market capitalization of 38.52 billion Mexican pesos ($2 billion). The shares closed at 11.440 pesos on Friday on the Mexican stock exchange.