President Reagan and West German Chancellor Helmut Kohl yesterday praised the agreement on East-West economic relations announced by Reagan on Saturday, as administration spokesmen mounted a defense of the accord against a chorus of critics.

There were indications in Paris that President Francois Mitterrand, despite an apparent initial French rejection, remained open to joining the other major industrial countries in the accord.

"Close consultation and cooperation on East-West economic issues is as vital to western interests as is the traditional cooperation on political and security questions," Reagan and Kohl said in a joint communique following their White House meeting.

It was the first time the two had met since Kohl succeeded Helmut Schmidt as chancellor, and the meeting came on the heels of the weekend announcement by Reagan of the East-West trade agreement and his subsequent decision to lift the sanctions against the Soviet natural gas pipeline.

Questions about Reagan's announcement built over the weekend as first France declared it was not a party to the announced accord and then, in contrast to U.S. claims of new departures, a number of officials of other European countries said the accord represented no major differences from previous accords on economic relations with the communist bloc.

"Substantial agreement" had been achieved, State Department spokesman Alan Romberg said yesterday in response to repeated questions. "There are only minor points of detail to be worked out.

"You will find that the kind of differences you are speaking of simply will not exist. Over time, things will work themselves out."

White House spokesman Larry Speakes said there had been consultations with Washington's negotiating partners throughout the week about a possible announcement and they "should not have been" taken by surprise.

"The judgment was made by the president, in consultation with his key advisers on this subject, that there was substantial agreement, and once there was he proceeded to announce it," Speakes said.

Other sources indicated that while the administration had pointed to a Saturday announcement, the final decision to go ahead was made at the last minute.

Speakes defended the impact of the sanctions, arguing, "They made our point that the president was serious. I think the allies understood that the president had strong convictions in this area on East-West trade and strong convictions on repression in Poland . . . .I think the message was sent forward to the Soviets. It enabled us to reach an understanding with the allies."

Speakes emphasized that the decision had nothing to do with the change of leadership in the Soviet Union.

Mitterrand followed up Saturday's sharp statement by his Foreign Ministry with much less strident comments yesterday.

"We don't refuse to participate in any dialogue," Mitterrand said of the East-West trade negotiations.

"We don't want France's independence of decision to be altered by conversations which have not yet been agreed to by responsible authorities. I am in charge of the interests of France and I will remain so," he said.

French Trade Minister Michel Jobert said more explicitly, "We would like the talks to continue, but the U.S. must understand that it cannot impose its will. President Reagan believes everything is settled: he has lifted the embargo and has Europe's approval. That is not quite the way we see it. You cannot agree to something that is not yet completed."

Reports from Paris indicated that the harshly worded statement issued Saturday was written by an aide to Mitterand and had not been seen by the French president.

It was understood in Washington that Reagan tried to telephone Mitterrand Saturday morning but was unable to reach him.

Mitterrand implied yesterday that now that Reagan has lifted the sanctions, a final decision on the trade accord might be possible.

"It was up to those who imposed the embargo to lift it," Mitterrand told reporters. "It's as simple as that. I have always said that it was not negotiable. Good sense has prevailed. Finally, the embargo has been lifted."

Much of yesterday's talks between Kohl and Reagan dealt with NATO issues and how to approach the new Soviet leadership, according to the communique.

The two men's public statements, however, were given over to effusive praise for the U.S.-West German relationship.

Reagan pointed to next year's 300th anniversary of the first Germans arriving in North America and appointed former national security adviser Richard V. Allen to head a commission to prepare for the occasion.

U.S. officials have displayed undisguised pleasure at Kohl's conservative government coming to power, and particularly over his outspoken support for the alliance defense posture and the introduction of a new generation of intermediate-range nuclear missiles in Europe in 1983.

The approach toward relations with the Soviet Union taken by Reagan and Kohl yesterday was harsher in tone than what might have been expected from Schmidt, Kohl's predecessor.

"The values and goals of the Soviet Union do not correspond to our own," the two leaders declared, calling on Moscow to "comply with internationally recognized rules of conduct."

"In this spirit," the joint statement said, "the president and the chancellor underlined their desire to improve relations with the Soviet Union. They are ready to conduct relations with the new leadership in Moscow with the aim of extending areas of cooperation, to their mutual benefit, if Soviet conduct makes that possible."

They pointed especially to Afghanistan as an "acid test of Soviet readiness to respect the independence, autonomy and genuine nonalignment of Third World countries and to exercise restraint in its international behavior."

Aides to Kohl later said he had urged Reagan to take advantage of the change in leadership in Moscow and seek a meeting with Soviet Communist Party leader Yuri Andropov, but only after the ground had been well-prepared.

Kohl and Reagan endorsed the arms talks under way in Europe--those on strategic and intermediate-range nuclear weapons in Geneva and those in Vienna on conventional forces.

"The goal of the United States and the Federal Republic of Germany remains to achieve a stable balance of both nuclear and conventional forces at the lowest possible level," the communique said.