Treasury Secretary James A. Baker III yesterday firmly rejected pressure from Common Market officials to link the question of a new multilateral trade round with efforts to control the dollar exchange rate.

Baker also rejected European calls for a U.S. commitment to a new study of the international monetary system before the summit meeting of the world's industrial nations in Bonn in May.

"The final say will be the president's at the summit," he said in an interview. "But it's our view that the two should not be linked. And everybody else, I think it's fair to say, is in favor of a new [trade] round without preconditions."

In a wide-ranging discussion covering domestic and international issues just prior to his first official trip abroad as Treasury secretary, Baker said he discounts "the rather anemic" first quarter 'flash' report on the Gross National Product that helped tilt the dollar down, and predicted that the United States economic recovery "can continue apace."

Baker will attend the ministerial meeting of the Organization for Economic Cooperation and Development in Paris April 11-12, a key preliminary to the heads-of-government economic summit in Bonn.

He conditioned his forecast of sustained economic growth on "getting some serious deficit reduction accomplished this year. And I'm a little more optimistic than I was [earlier] on that score."

Baker said that the recent decline of the dollar in foreign exchange markets -- it's down about 9 percent against major currencies since a high point March 5 -- is due mostly to foreign attention to the first quarter flash report, and to the Ohio savings and loan closings two weeks ago.

According to the "flash", or preliminary GNP report, the economy grew at a real rate of only 2.1 percent in the first quarter, compared to a revised figure of 4.3 percent in the fourth quarter of 1984. Baker's point is that these preliminary figures are frequently revised substantially.

Baker made it clear that the Reagan administration is not disturbed by the easing of the dollar against other leading currenciies. "What you've seen happen, in my view at least, is you've seen the market work . . . ," he said. Other high Reagan administration officials predict that the dollar will remain strong, even if below recent peaks.

Official statements and "leaks" from European capitals in the past several days indicate that some nations at the Paris OECD session and the Bonn summit will press hard for changes in the international monetary system designed to force down what Europeans say is an "overvalued dollar."

But high administration officials confirm that the Reagan administration is not planning to study or endorse significant changes in the international monetary system.

At a breakfast with reporters earlier this week, President Reagan said that while he continued willing to talk about international monetary reform -- an issue pressed especially by French President Francois Mitterrand -- the issue was not a top priority on his agenda.

Baker would not comment directly on the Senate's 92-0 vote on Thursday, calling on the president to retaliate against Japanese protectionism, although other sources said the White House feels it would be unfortunate if the Congress attempts to respond to Japan with openly protectionist devices of its own such as an import surcharge.

But Baker did say, cryptically: "I'm not sure the Japanese realize the seriousness [of how the trade issue is regarded] on the Hill."

Baker rejected the notion, reported to be widespread in Europe, that the forced closing of 70 S & Ls in Ohio reflects a general weakness in the American financial structure. He said, first of all, that quite a few of the Ohio thrifts had now been reopened. "I don't think there's a fundamental illness in the nation's banking system," he said.

He acknowledged that many banks -- notably some in Massachusetts, Texas, and in agricultural areas and in the energy sector -- have recently had problems. But he doesn't believe those problems are due, as others suggest, to a lack of regulation or lack of supervision.

"My view is that those situations occurred as a result of people betting that inflation was here to stay, which was a reasonable bet before Ronald Reagan came to town," Baker said.

Speculation on ever-rising farmland prices is held to be the problem for agricultural banks. And larger banks, such as Penn Square, got in trouble betting on the prospect of oil going to $40 a barrel or more. Energy loans are also reportedly the main source of current troubles in some large banks in Baker's home state, Texas.