There are mounting indications that the Chilean government may soon accede to international pressure by curbing the nearly absolute arrest powers of DINA, its dreaded secret police.

The reports came as U.S. Assistant Secretary of State of Latin American Affairs. Terence Todman, arrived here today for the first high-level contact with the Chilean government during the Carter administration, which has stressed the need for Chile to improve its human-rights image.

According to the reports from diplomatic and Catholic Church sources and from prominent regime supporters, the military government of President Augusto Pinochet is expected to quietly ease human-rights restrictions next month.

This would concide with the expiration of the state-of-siege decress that are the legal basis for DINA's power and for the restrictions on habeas corpus and political and press freedom.

DINA's arrests without charges and its operation of secret prisons have been blamed for the disappearance and torture of hundreds of people. State Department officials have said that DINA actively is a specific area of U.S. human-rights concern in Chile.

Human-rights advocates said that some informal restrictions may already have been put on DINA's repression of dissenters this year, although its structure remains intact.

Political arrests, which once averaged more than a hundred a month, have dwindled to a handful since January, they say, and recently the Chilean press has been allowed for the first time to publish details of DINA abuses.

Todman's visit has been described here as part of Carter's human-rights policy toward Latin American military governments.

Another U.S. human-rights spokesman, Ambassador Allard Lowenstein, left Chile this morning after a day of talks with Chilean leaders and human-rights spokesmen. There was a notable absence of expressions of hostility about Lowenstein's activities here, in contrast to past Chilean protests of U.S. human-rights initiatives regarding Chile.

Todman is expected to meet with prominent non-government figures such as former President Eduardo Frei, leader of the outlawed Christian Democratic Party and Raul Cardinal Silva, the country's leading spokesman for the defense of human rights, as well as with senior government officials. He is also to meed former presidents Jorge Alessandri and Gabriel Gonzalez, who are supporters of the military government.

A Chilean general who declined to be identified said in an interview that "you can expect changes in the short term" that would improve Chile's human-rights image. He said that the military is in full agreement with Pinochet's recent announcement of limited elections by 1985, adding that if conditions permit the election timetable could be moved up.

Diplomatic sources said reports are increasing that the government is about to lift DINA's arrest power and restrict it to intelligence-gathering activities. A church official close to Cardinal Silva said Chilean bishops have gotten "many promises recently that the DINA is going to be changed."

The measures are expected to take effect Sept. 11, the fourth anniversary of the military coup that brought Pinochet to power. The anniversary also means the expiration of the state-of-siege decress.

The sources said there is a growing consensus among moderates in the government and in the armed forces that there is no longer an imminent danger of leftist subversion and that non-renewal of the state of siege would pay major dividends in Chile's international relations.