An American banker here, asked if he thought Bolivia's military government would keep its promise to call elections in 1980, replied "I hope to God not."

For the first time since independence, he continued, Bolivia has stability and a favorable business climate it never achieved while political parties were operating.

Businessmen are happy in Bolivia, there is no question about it. President Hugo Banzer Suarez, a tough army general who took power in a coup in 1971, now holds this century's record for permanence in office here. He presides vigilantly over one of the country's rich deposits of more than a dozen valuable minerals.

Bolivia always has lived off its mines. It is said that the silver from Potosi capitalized Europe at the turn of the century, but the proceeds only lined the pockets of the revolving-door governments and their friends. To this day, two-thirds of the 5.6 million inhabitants are impoverished Indians, most of them illiterate and outside the money economy, outside politics, and outside of the cities.

There has been no overnight miracle here and a barely decent standard of living still may be decades away. Stability has been achieved at the cost of repressive police tactics, widespread arrest and torture and the exile of at least 5,000 persons, according to sources in the Catholic church. Unions and political parties are silenced, and the discovery of frequent plots, coup attempts and subversive groups continues to be used as justification for the strongarm methods.

But there has been an undeniable change in attitude since Banzer came to power on the part of the financiers.

A total of $1.2 billion in foreign loans has entered Bolivia since 1971 from the International Development Bank, the World Bank, the U.S. Export-Import Bank, private bank consortia and individual governments. Domestic investors have brought back much of their capital from overseas, lured by high interest rates and guarantees, and everywhere there are signs of it; Soaring high-rises, glossy new banks, hotels, flashy cars and new roads for them to travel.

Banzer, in a written response to questions, called this new attitude his most important achievement so far; "For a long time one frustration after another created a national attitude of defeatist fatalism. But now the country can see the results of its joint effort and that attitude has been transformed to one of positivism and optimism."

It is the awesome uptapped potential here in agriculture and minerals that has the money men interested, if somewhat uneasy about the vast investments that will be needed to develop it all. The government estimates that 90 per cent of the vast agricultural and pasturelands of Beni and Santa Cruz provinces are untouched, and land is going at 80 cents an acre in some places. Similarly, only 5 per cent of the known reserves of minerals are tapped although there are 5,000 mines of various sizes around the country. No intensive exploration for other deposits has even been attempted in the last 25 years.

At the moment, the government's ambitious $3.5 billion five-year plan focuses on mining, agriculture and the combined flow of oil and natural gas as the three keys to the future. tin, which was the roller-coaster supplier of nearly half the country's income as recently as 1970, has been relegated to an equal place with oil, just as tin prices have reached record levels.

If Bolivia has its way as the second largest producer, tin prices will edge even higher. A recent meeting here of the four top suppliers - Malaysia, Indonesia, Thailand and Bolivia - produced agreement to push for a stable high price at the International Tin Conference meeting this month.

It is unlikely that the country's 35,000 miners will see much of whatever increase occurs, however. The army occupied the major mines during a bloody June strike, arrested and expelled most of the union leaders and refused to grant the demand for an 80 per cent increase - from about $1.50 to $2.80 per day. Government officials said fringe benefits and company stores mean the miners earn much more than that already, and after breaking the strike in 23 days offered a 30 per cent rise.

President Banzer, however, demonstrating his skill in measuring the limits of his cities' tolerance, then announced a $138 million social benefits plans for the miners and a housing construction program of $60 million.

The oil sector is also having its problems. Only one of the 11 foreign company contract groups. Occidental, has had any luck in finding new deposits, and seven of them have pulled out of Bolivia after drilling only one dry well. An industry source estimated that the foreign companies had spent $100 million in the hunt over the past four years. The state oil company, YPFB, has kept the most promising areas for itself, but also brought in one field after a foreign company had abandoned it.

Still, Bolivia export 22,000 of its slim 40,000 barrrels-a-day output, a fact that turned the economy around in 1974 and ended the dependence on tin. The five-year plan predicts a tripling of known reserves and production of 18,000 barrels a day by 1980, figures the industry insider said were long shots but possible. "Nobody really knows what's out there yet," he said.

"The government is confident of its strength now," said the Rev. Jose Gramunt, controversial director of Radio Fides. "They used to call me and complain when I criticized, but not any more. They don't care. I've never seen so many satisfied businessmen."