South Korean students today called a halt to their anti-government demonstrations, at least temporarily, and the streets of Seoul were quiet after three days of often violent protests.

Student leaders from 28 universities agreed after an all-night discussion to stay off the streets at least through the weekend, hoping that the government would respond to demands for quicker political reforms.

Those demands were promptly taken up in the political arena when two prominent opposition leaders insisted on a political timetable that would see a presidential election before the end of this year.

The two leaders, who have been feuding for weeks between themselves, closed ranks long enough to adopt the students' demands. Kim Young Sam and Kim Dae Jung also called for the immediate lifting of martial law, the resignation of the prime minister, and the prompt retirement of a general who has exerted increasing power since the assassination of president Park Chung Hee.

Although the students went back to their books, there was no guarantee that the days of street protests were over. Some indicated that the demonstrations would be resumed next week if the civilian government has made no specific response.

Informed sources said the government was preparing concessions that would meet some of the students' and opposition party's demands. There was no indication when they would be disclosed. Government officials speculated it would not be before next Tuesday when the National Assembly meets.

President Choi Kyu Hah cut short a foreign travel schedule by one day and returned to the capital late tonight. An indecisive leader who exerts little personal power, Choi is expected to follow the advice of Cabinet and military leaders. Sources reported that there was still considerable internal debate over how far the government would go.

Prime Minister Shin Hyon Hwack last night coupled a vague offer of quicker reforms with a warning that students should keep off the streets. His speech was greeted with derision by many students because of its lack of specific promises.

In interviews today, the students gave a variety of reasons for their temporary truce but a major one was their inability to get broad public support for street demonstrations.

They had hoped initially that workers and others would join the ranks to either topple the government or force it to grant quick concessions. Although bystanders occasionally joined the street marches, there was no big rush by citizens generally to go along.

Neither the public nor the press gave support, said a Yonsei University junior, Chung Suk Ho. Instead, he said, the students were accused of interrupting business and traffic and causing further damage to an already weak economy. He and other Yonsei students said the time had come to try to bargain with the civilian government.

The joint statement issued by opposition leaders Kin Young Sam and Kim Dae Jung was something of a surprise because they have been engaged in a bitter factional struggle. Both want to run for president.

They called for a reform schedule that would provide for adopting constitutional amendments and holding a presidential election by the end of this year. The government so far has vaguely promised a constitutional referendum this fall and elections next spring.

They also called for the resignation of Prime Minister Shin and the immediate retirement from the military of Lt. Gen. Chon Doo Hwan. Chon headed a group of generals who grabbed military power last December and has since been appointed director of the Korean Central Intelligence Agency.