As the West German election campaign reached its climax, Chancellor Helmut Kohl and his Social Democratic rival, Hans-Jochen Vogel, said today that the United States would soon offer a compromise on restricting medium-range nuclear missiles in arms talks with the Soviet Union.

The separate comments by the two leading candidates for chancellor reinforced contention here that Washington is now convinced of the need to achieve rapid progress toward an arms accord--once the elections are held--to defuse the risk of violent demonstrations in Western Europe against deployment of new missiles later this year.

At a news conference today culminating his campaign before Sunday's vote, Kohl said, "I assume, though I cannot name a date, that the Americans will in the foreseeable near future take further steps to advance the negotiation timetable."

He added, without elaboration, that the time frame for the arms talks was becoming critical but that he was "cautiously optimistic" about chances for a successful deal to be struck with the Soviets.

Vogel, in his appearance before reporters to cap his election drive, contended later that "a constructive counterproposal" was anticipated from Washington "next week or the week after."

In Washington, administration officials said no decision had been made on a new U.S. proposal, but they noted that President Reagan is to meet with his secretary of state and other advisers this weekend.

During an intense two-month campaign dominated by impassioned debate over the missile issue, Vogel repeatedly urged the United States to respond to Soviet leader Yuri Andropov's proposal, in a speech Dec. 21, that would reduce the number of Moscow's medium-range nuclear weapons to the 162 missiles deployed by France and Britain.

Washington, Paris and London, as well as the Kohl government, rejected the Andropov plan, saying the French and British missiles were only national deterrent forces. But Vogel and other Social Democrats have accepted Moscow's view that such weapons must be taken into account in the Geneva negotiations.

In a live television debate last night, Kohl and the other two party leaders in his ruling coalition, the Christian Social Union's Franz Josef Strauss and the Free Democrats' Hans-Dietrich Genscher, sharply attacked Vogel for his stand on missiles.

Vogel said that if he were elected, one of his primary objectives would be "to make the stationing of new missiles superfluous," even if that meant delaying the December deployment, under current NATO plans, to provide more time for negotiations--or installing the missiles on submarines instead of land.

Kohl accused his challenger of reneging on a commitment made by the Social Democratic-led government of Helmut Schmidt to the NATO decision, approved unanimously by member governments in 1979, to proceed with deployment of modern Pershing II and cruise missiles by the end of this year if negotiations failed to secure Soviet reductions in nuclear-tipped rockets aimed at Western Europe.

Pressed repeatedly by Kohl and Strauss to declare his intentions as chancellor if the arms talks did not succeed, Vogel sought to dodge a direct answer but finally was compelled by one of the two journalists serving as moderators to state his position succinctly.

"In the most extreme case that the Soviet Union retracts its previous movement, in the most extreme case that further far-reaching proposals by our American friends are rejected, then I would not rule out the possibility" of deploying the missiles, he said.

During the debate, which lasted more than three hours, Vogel's three opponents charged that Vogel courted the antinuclear, ecological Greens Party and allowed the Social Democrats to drift toward a more neutralist posture in foreign policy.

Denouncing the "foolish anti-Americanism in your ranks," Kohl told Vogel that "important parts of your party are calling the alliance into question."

Strauss, the Bavarian premier who hopes to replace Genscher as foreign minister if the conservatives win the election, also criticized the Social Democrats for "so many spiteful statements against the Americans."

Vogel sought to rebuff such remarks with stoic humor, and responding with attacks on Kohl for not doing more to curtail unemployment. He accused the chancellor of "most serious violations of social justice" and said the conservatives' economic policy was tantamount to redistributing wealth from the poor to the rich.

Vogel insisted that the state must play a more dominant role in reducing the country's record unemployment of 2.54 million, or 10.4 percent of the work force, and that the Social Democrats wanted to press for a shorter work week and early retirement to ease pressures for jobs.

Kohl, Strauss and Genscher all rejected the notion of more state programs, expressing doubts that such an approach could create many permanent new jobs.

The chancellor also contended that with five months in office, he could not be held responsible for "the inherited burden created by 13 years of Social Democratic mismanagement." But he also noted that there were strong signs of an upswing that augured a new boom.

Toward the end of the heated debate, Kohl tried to strike a more statesmanlike posture by emphasizing that following the Sunday election, the country must put aside ideological bitterness and "return to democratic togetherness." Turning to Vogel, he said: "We are opponents, but not enemies."

None of the four politicians seemed to emerge with his stature noticeably enhanced by the debate. Moreover, most election polls indicate a relatively small number of undecided voters whose choice might have been affected.