Luis Herrera Campins, inaugurated today as president of South America's most durable democracy, pledged that Venezuela will remain a reliable source of petroleum for the United States and Europe and hinted that he may even approve a plan to increase production here by as much as 400,000 barrels a day.

Herrera said the industrialized nations, particularly the United States, which imports about 1 million barrels a day of Venezuelan crude, should appreciate Venezuela's current all-out effort to produce near capacity to help overcome the worldwide oil shortage caused by the revolution in Iran.

Since the beginning of this year, Venezuela has been producing more than 2.3 million barrels a day, just 100,000 barrels a day short of its capacity and more than 100,000 barrels a day above its normal production. Because of increased production and increased prices, Venezuela, which has serious balance of payments problems, will earn an additional $1 billion this year.

Most of the exports go to New England and the Middle Atlantic states, which depend almost entirely on Venezuela for their heating and fuel oil requirements.Although this country increased its oil price by 15 percent on March 1, some observers here believe Venezuela could have increased it even more -- especially by cutting production at the same time.

Herrera, 54, a lawyer and university professor who beat the candidate put forward by outgoing President Carlos Andres Perez's Democratic Action Party in December, said he was worried about straining Venezuela's current production capacity by producing so close to its limit.

But he also said that his new government "will have the strength necessary to add to the potential production [capacity] in accord with the amount of reserves and to accommodate a development strategy consonant with the best interests of the Venezuelan people."

Diplomatic sources said Herrera seemed to be indicating support for a plan already approved by his political party, Copei, which is similar in ideology to Christian Democratic parties, to invest in new technology and equipment with the aim of increasing production by 400,000 barrels a day. Such a decision could help the United States while increasing Venezuela's revenues.

Herrera also said during his inaugural address that he favors an "investigation" of production possibilities of Orinoco tar fields -- crude so thick that it cannot be raised with current technology. Eventually it is expected to add signficantly to Venezuela's reserves, which otherwise will be depleted within 20 years.

Before the year 2000 Venezuela must build a solid economic base -- even if the Orinoco fields become viable and productive, according to most observers. Under the Perez government, which benefited enormously from the 1973 quadrupling of oil prices, Venezuela began a series of costly development projects, such as steel and aluminum mills, designed to replace oil as the country's only important export.

Herrera focused his successful campaign on the corruption, waste and inefficiency that have accompanied Perez's crash industrialization program -- as well as the old government's inability to stop inflation, which last year jumped officially to 7 percent but which many informed observers believe was actually closer to 20 percent.

During his campaign and again today, Herrera spoke emotionally about Venezuela's millions of poor families who have benefited only marginally from the oil boom and who have grown increasingly frustrated at the disparity between their lives and those of the rich.

The new president promised to improve educational opportunities and health care for the poor, implement measures to stop increasing street crime and drug use in the cities and generally improve government delivery of basic services, such as water and electricity.

Herrera said he inherited a country "mortgaged to the hilt" as a result of massive borrowing abroad by the Perez government and policies that led to Venezuela's balance of payments deficit last year that was its largest ever. Herrera said he fully recognizes that he must institute austerity measures in the months ahead to correct the country's economic "disequilibrium."