Mexican President Felipe Calderon gave the green light to several of his Cabinet members to resign and vie for the presidential nomination of the ruling conservative National Action Party, or PAN.

"They can leave anytime they want ... The thing is for them to tell me," Calderon, who is barred from re-election, told Milenio Television's Ciro Gomez.

The interviewer had asked when the secretaries of finance, Ernesto Cordero, labor, Javier Lozano, and education, Alonso Lujambio, could leave their posts to seek the PAN nomination.

Several politicians from the PAN, as well as from the opposition PRI and PRD parties, are already shaping their strategies to become their parties' presidential nominees.

The parties' internal election processes begin in October and the respective candidates should be decided upon before the end of the year.

For the PAN - besides Cordero, Lozano and Lujambio - Congresswoman Josefina Vazquez Mota, Sen. Santiago Creel and Jalisco Gov. Emilio Gonzalez, among others, have expressed their desire to vie for the nomination.

Regarding the list of aspirants, Calderon said in the interview with Milenio that "it must be cut down," but he added that a democratic process of selecting the nominee will strengthen the person who ultimately becomes the PAN's candidate.

Analysts and politicians have criticized the fact that Cabinet secretaries have an advantage over others due to their constant media exposure, and so they should resign their posts to participate on equal terms with other PAN aspirants.

Mexican presidents are limited to a single six-year term.