By Miguel Angel Gutierrez

MONTERREY, Mexico, June 25 (Reuters) - Mexican President Felipe Calderon will propose a tax reform in September aimed at raising Mexico's low tax take by widening the taxpayer base, a member of his inner circle said on Friday.

Former presidential secretary Cesar Nava, who is now a ruling party candidate for a seat in the lower house of Congress, did not provide details on the plan to widen the tax base.

Nava said the government would not seek to raise tax on goods and services and would offer targeted tax cuts for businesses to help secure the passage of the legislation.

Calderon's National Action Party, or PAN, is headed for a setback in congressional elections on July 5, meaning the government will need closer negotiation with opposition parties to pass laws.

Mexico is under pressure to raise its tax revenues and reduce a dependence on oil exports as the country's crude production wanes. Ratings agencies are pondering a downgrade to Mexico's debt without an improvement to its fiscal outlook.

Nava told reporters the president will also propose trimming government and Congress running costs in the tax proposal, which will be part of the 2010 budget bill submitted in mid-September.

"I don't see, or propose, changes to the value-added tax. We can't ask people for more sacrifices," said Nava, who is widely seen becoming the leader of Calderon's conservative National Action Party, or PAN, in the lower house.

Nava is an up-and-coming PAN politician expected to push Calderon's agenda in Congress.