Kuwait announced a 25 percent cutback in oil production yesterday, adding an element of uncertainty to a petroleum mark that had begun to relax a bit because of the current glut in supplies.

The announcement by Kuwait's oil minister, Sheik Ali Khalifa Sabah, also sharply focuses attention on neighboring Saudi Arabia, which has said it will continue producing an extra million barrels of oil a day only through April.

The combination of extra Saudi production and cutbacks in demand in the major consuming countries has resulted in a sharp drop in prices in the so-called "spot" or one-time purchase market, and also had led some experts to anticipate a softening in the "premiums" charged regular customers by some members of the Oranization of Petroleum Exporting Countries.

Kuwait's formal announcement yesterday that it is reducing output by 500,000 barrels to 1.5 million barrels daily is expected by experts to have a marginal effect on this price trend, although it is the first major cutback formally announced by an OPEC country and sparked fears that it could be followed by others, particularly the Saudis.

The immediate supply effect of the formal announcement will fall on Japan and other Asian countries, with some impact also expected in Europe. The United States gets none of its regular oil supplies from Kuwait.

"The market can absorb the Kuwaiti cutback, but it is not clear in a psychological sense whether it could weather a million barrel cutback by Saudi Arabia," one U.S. official said yesterday.

The Saudis have put out hints of their intentions that go in both directions, this official said.

Saudi Arabia increased production by a million barrels a day to 9.5 million to make up for a shortfall from Iran following the political upheaval in the country last year. Saudi Arabia has said it will keep production at the higher level through April.

The Kuwaitis have amassed huge monetary surpluses and have suggested for several months that they were preparing a cutback to conserve resources for the future. They have warned companies that get oil from them to expect less under new contracts.

Gulf Oil, which currently gets 500,000 barrels a day from Kuwait for sale in the Far East, has been told it will receive only 160,000 barrels daily under a new contract that comes into effect in a month, according to a company official.

It is in the price area that the Kuwaiti announcement caused some ripples yesterday among energy experts.

While several experts stressed that Kuwait's cutback has long been expected and calculated in price and supply estimates, there was still a small not of concern.

John Lichtblau, of the Petroleum Industry Research Foundation, noted that there will be a surplus even with the Kuwaiti cutback but also said that prices "could be affected" had supplies continued to increase, adding to the world glut.

OPEC prices now range from $26 to $34 a 42-gallon barrel, with countries charging the highest figures reaching them by charging "premiums" to a number of their customers. Lichtblau said that these "premiums" could have been affected had oil supplies continued to grow.

"From their [the Kuwaiti] point of view, it makes sense," Lichtblau said, "but from a consumer perspective, maybe 2 million or so would have been better."

In a global assessment yesterday before the Senate Foreign Relations Committee, Energy Department Deputy Secretary John Sawhill said that "the outlook for the 1980s is . . . for temporary relief from the price pressures experienced in 1979, barring a severe supply interruption or cutbacks" beyond expected levels.

Since Kuwait had signaled it planned a cutback, yesterday's announcement was calculated into Sawhill's assessment. What Saudi Arabia will do, however, remains a question mark.

West German Economics Minister Otto Graf Lambsdorff warned last week during a visit to Washington that Arab oil producers will steadily reduce the amounts of oil they sell, buttressing the current world price structure.