Iran's parliament is scheduled to begin discussing the U.S. hostage issue Sunday amid reports that it will likely add to the four conditions listed by Ayatollah Ruhollah Khomeini for the release.

After weeks of delay, however, the debate could be further postponed by the unresolved political crisis and intensified border fighting with Iraq.

Parliamentary sources said a reply to 187 U.S. congressmen, who have appealed in a letter for release of the 52 captives, had been agreed by the Foreign Relations Commission of the Majlis, or parliament, and might be read to deputies Sunday.

An Algerian envoy delivered a letter in which all the families of the American hostages "had a say" to Iran's parliament, Tehran Radio said. It did not disclose the letter's contents.

The state radio today continued to broadcast Khomeini's message, in which he told Moslem pilgrims yesterday that the hostages could be freed in return for the return of the late shah's property, a pledge of U.S. noninterference in Iran, cancellation of American claims against Iran and an unfreezing of Iranian assets.

Newspapers carried the text without comment, but one highly informed source close to the Foreign Relations Commission predicted that deputies would call for additional conditions.

"We will definitely want an American apology for their crimes under the shah's regime," the source said. "We have already compromised enough, such as the fact that we did not ask for a trial," he said.

The commission, in a draft reply to the U.S. congressmen earlier this month, demanded the return of Iranian assets in the United States and a full admission by the White House of former American "crimes."

Khomeini's message marked a shift away from his threat, issued two weeks after the embassy seizure, that the hostages would be tried if the deposed shah were not returned to Iran.

The shah's death in Cario last July put an end to the controversy, and observers speculated today that the increasing division in the country may have softened Khomenini's position.

President Abol Hassan Bani-Sadr and Prime Minister Mohammed Ali Rajai are still at loggerheads about the Cabinet, while the border conflict with Iraq charged that Iran launched the latest bormonths of skirmishes.

Reports from both Iran and Iraq indicated that the border conflict was heating up, with new fighting swirling on the frontier near the Iraqi city of Basra, United Press International reported.

Iran claimed to have killed 100 Iraqis in the fighting, and Tehran radio, monitored in London by the BBC, said bani-Sadr personally toured the battle fronts.

(Iraq charged that Iran launched the latest border attack yesterday and that fighting was continuing with planes, tanks and artillery. An Iraq military spokesman said eight Iraqis were killed and that "we retaliated heavily." The Iranians "had to use six ambulances and nine buses in taking their casualties," he said.

In another development, the former Iranian Air Force chief, Maj. Gen. Amir Bahman Bagheri, was arrested at Tehran's airport today before he was due to leave for France, Revolutionary Guards said.