Soviet President Leonid Brezhnev and West German Chancellor Helmut Schmidt joined in a call here last night for concrete international measures to speed up an end to the arms race and rescue the stagnating process of detente.

Ending three days of formal summit talks here, the two leaders stressed the "supreme urgency" of arms control.

"Agreement on further steps in the field of disarmament and arms control must be speeded up so that the process of dentente is aided, and not hampered, by developments in the military field," they said.

The Soviet leader also addressed the West German people last night in a 20-minute nationally-televised speech in which he made a strong public appeal for curbing the arms race.

"We are at a decisive point in world events," he said. "It is no secret that this process (of detente) has slowed down and the main reason is the failure to stop the monstrous arms race.

"The past prevails on us to learn the lessons of history in an effort to avoid new tragedies. Time is short. Every lost day, every postponement, can harm the human race and us all."

Despite his personal appeals and lofty rhetoric, there was no apparent progress here on arms questions, specifically Bonn's concern about Soviet armament buildup in Eastern Europe.

Following his television appearance which marked the end of his official visit, Brezhnev flew to Hamburg with Schmidt to spend a fourth day in West Germany as the private guest of the chancellor. A final communique on the visit is to be issued today.

The arms control call came in a joint political declaration that also included a 25-year economic cooperation agreement. The latter was termed by Schmidt as being "without parallel in recent world history" but was viewed with considerable skepticism by West German industrialists and businessmen.

At the signing ceremony last night, Brezhnev, 71, his face with its now familiar puffy look and his speech somewhat indistinct, was nevertheless in good spirits and described the talks as "necessary, rich in content and useful."

The economic agreement - which is actually a framework for future cooperation - was the most tangible accomplishment to come out of these summit talks. It is important on the surface, yet it can also be misleading and deceptive, in the widespread view of West German officials.

The agreement actually runs for an intitial 10-year period and is renewable for three successive five-year periods, which ties into Soviet five-year planning. It is not a specific trade agreement but rather a vague outline of further efforts to cooperate wherever possible in construction of new industrial plants, raw material development, energy exploitation and industrial and consumer goods technology.

For Bonn, the agreement is politically important because it generally eases tension in central Europe between two formerly bitter enemies and because its unprecedented duration provides some tangible link and continuity to new Soviet leaders after the Brezhnev era ends.

For Brezhnev, the agreement allows him to bring back some evidence that his political gamble at home on reliance on Western technology and massive credit to help build up the Soviet economy is still working.

The new arrangement does appear to commit both parties, but in effect only West Germany, to "take efforts to insure middle- and long-term financing" of would-be projects.

The catch to the agreement is that the Soviet government can make deals, but on the West German end all projects are carried out by industry. It is West German industry that is worried by recent trends in Soviet payment.

West German trade with the Soviets has boomed in the eight years since the two countries signed thier normalization treaty. Trade has more than quadrupled in the past six years to a level of more than $5 billion last year, a figure almost three times higher than U.S.-Soviet trade.

Bonn is now Russia's largest and most important trading partner in the West, with West German firms building pipelines in Siberia, steel plants in Kursk, trucks along the Kama River, chemical plants and rolling mills in several places. When travelers go to the Moscow Olympics in 1980, the new air terminal will be West German-built.

Still, the Soviets only account for 2.2 percent of West Germany's vast export business, so the Soviets are less important to Bonn than Bonn is to Kremlin. Trade has actually dipped a bit this year, as the Soviets try to cut their huge deficit.

What worries West German industrialists most is increasing Soviet demands for "compensation" deals in which imports are paid for by sending Soviet products, rather than hard cash, to West Germany.

The new agreement calls for more such deals wherever "mutually agreeable." Roughly 10 percent of the trade is already in such a barter deals and the West Germans say there is a limit to such payment because, aside from certain raw materials, Soviet goods cannot compete with Western goods on West German markets. Even the exports by Russia of so many raw chemicals has West Germany's big chemical labor unions concerned.

Otto Wolff von Amerongen, chief of the powerful West German Industry and Trade Council, said yesterday the new treaty was "not an historical agreement, as the Bonn government called it. There was scepticism here generally over the results of the Brezhnev trip.

The influential Frankfurter Allgemeine Zeitung stressed the lack of concrete progress achieved on key issues, such as disarmament, in a front-page editorial today. It said the visit was not likely to go down as an event of historic importance. "The reality is far more prosaic," it said.

Referring to the surprise with which Bonn officials were caught when Brezhnev, after years of delay, finally decided to come here, the paper said "four weeks ago, no one even had the idea of a long-term economic accord which, having been rapidly stitched together, is now being portrayed as a miracle."

The timing of Brezhnev's trip was seen here as linked to the forthcoming session of disarmament at the United Nations in New York and also perhaps to exploit recent strain in U.S.-West German relations.

Brezhnev was expected to place a heavy emphasis on calls for disarmament, even thought the Soviet build-up in Eastern Europe is of major concern to Western leadrs.

Top levell aides to Schmidt said privately that the chancellor had no success trying to persuade Brezhnev to cut back on either tank armies or nuclear-tipped missiles aimed at Western Europe in exchange for President Carter's deferral of production of the neutron bomb meant to counter the numerically superior tank armies.

The joint declaration signed by the two leaders, aside from pledging a commitment to greater cooperation and to detente, also said no country "should seek military superiority."

The leaders "proceed from the assumption that approximate equality and parity suffict to ensure defense," it said.

There were some suggestions that this phrase indicated some progress in convincing the Soviets that they ought to reduce some of the Warsaw Pact forces in central Europe - which outnumber the West by roughly 150,000 troops - to achieve greater balance with the West.

"That is an interesting nuance," an aide to Schmidt said privately.

But officials quickly pointed out that the Soviets do not accept the Western estimates of Warsaw Pact troop strength and have argued at the East-West troop reduction talks in Vienna for years that there already was approximate parity between East and West ground forces.