Spain urges oil firms to cap pump prices, fight inflation

* Energy minister to meet BP, Cepsa, Repsol execs

* Soria: "Everyone has to pull their weight"

* Govt worried by inflation's impact on pensions

MADRID, Sept 12 (Reuters) - Spain's energy minister said he would urge oil companies on Wednesday to cap petrol prices at the pump to help efforts to control inflation in the country.

Jose Manuel Soria said he would make his appeal during a meeting on Wednesday afternoon with executives from Spanish oil firms Repsol and Cepsa and Britain's BP - which together represent about 80 percent of the country's gasoline market.

"This is no small matter," Soria told Onda Cero Radio in an interview.

"We're going to put forward the idea that in times of adjustments like these everyone has to pull their weight and that's what the government is asking of the sector," he added.

Spanish consumer prices rose 2.7 percent in August after 2.2 percent rise in July, due mainly to higher gasoline prices. Consumer prices are likely to rise again in September after a recent 3-percentage-point hike in value-added tax.

The impact of inflation on pensions - which are raised in line with consumer prices - is a major concern for the Spanish government as it tries to keep spending down and avoid an expensive European bailout.

Soria did not say what incentives the oil companies might have to cut their prices and help in his fight against inflation.

But the government announced last week it was considering taking tax measures or adjusting contracts with oil companies to reduce operators' commercial margins, which it said were higher than the European average.

Spanish brokerage N+1 Equities said it might be hard to put such measures into practice.

"Taxes would not reduce the sale price for consumers unless they (the oil companies) cap margins," the brokerage said in a research note on Monday, adding that the oil companies would have to agree to any changes to contracts.

The brokerage advised the government to make it easier for companies to open more petrol stations, a move that would increase competition.