For the second time in less than a year, a South Asian country has rejected the appointment of a high-ranking diplomat assigned by the State Department to the U.S. Embassy there.

Afghanistan's Soviet-backed government touched off the latest diplomatic dispute by refusing to grant a visa to Archer K. Blood, a veteran South Asia expert who was to serve as charge d'affaires, the top post at the embassy in Kabul.

The State Department has branded Afghanistan's action "an unacceptable...breach of practice" and has retaliated by imposing travel restrictions on diplomats serving in Afghanistan's embassy in Washington and its United Nations mission in New York.

Afghanistan told the department Feb. 20 it was rejecting Blood's visa application because of contacts he reportedly had with Afghan dissidents during his service as deputy mission chief at the U.S. Embassy in New Delhi from 1977 to 1981. Accounts in the Indian press said Blood's rejection also stemmed from contacts he is said to have had with former Afghan president Hafizullah Amin, whose Marxist government was overthrown in the December 1979 Soviet invasion.

Last July, India barred George G.B. Griffin as political counselor to the embassy after leftist groups accused him of being an agent of the Central Intelligence Agency. The United States, which denied Griffin was a CIA agent, retaliated by blocking India's choice to fill the same position at the Indian Embassy here. The positions were filled only last month, a department spokeswoman said yesterday.

Some U.S. officials believe Moscow was responsible for both rejections, which are considered highly unusual departures from normal diplomatic practice. The official Soviet press attacked Griffin while he was stationed in Kabul for disseminating information to Western reporters about the Soviet invasion of Afghanistan, and Pravda was one of the first to accuse Griffin of CIA connections. India denied that the Soviet attack was behind Griffin's rejection.

In Blood's case, one State Department official here said that while the Soviets want the United States and other Western governments to maintain diplomatic missions in Kabul to confer legitimacy on the Soviet-installed government, they probably did not want someone of Blood's expertise and contacts to be stationed inside the country. The Soviet Union has an estimated 90,000 troops in Afghanistan fighting Moslem guerrillas.

Blood has served twice in the Kabul embassy, in the mid-1960s and for a six-month emergency stint in 1979 following the murder of U.S. ambassador Adolph Dubs by terrorists. It was during this second tour that he was said to have had contacts with then-president Amin.

A State Department official who asked not to be identified confirmed this week that Blood had met with Afghan dissidents and with Amin. But the official said the meetings were routine for a diplomat charged with monitoring the country's political climate and denied that they constituted any interference in Afghanistan's internal affairs.

"It's his job to see the president of the country he is working in and to talk to people, and what he did was totally in line with what any reasonable government would expect," said the official. Blood, who is currently assigned to the State Department here, did not return a reporter's phone calls.

The United States has withdrawn almost all of the estimated 200 diplomats, support personnel and aid staff who were stationed in Afghanistan. All that remains is a skeleton staff of 20, most of them support personnel and security guards, who stay on in Kabul to maintain a U.S. presence there.

The department in a written statement said Afghanistan's stated reasons for Blood's rejection were "irrelevant and immaterial" and said it has made protests to both the Afghan Foreign Affairs Ministry in Kabul and to the embassy here.

It also has imposed travel restrictions on Afghan diplomats similar to those imposed on Western diplomats in Kabul. In Washington, Afghan diplomats cannot travel more than 12.43 miles from the center of town--the Capitol dome--without prior written permission from the department. In New York, the limit is 25 miles from the center of Columbus Circle in Manhattan.

The embassy's top official, First Secretary Salem M. Spartak, was out of the country this week and unavailable for comment.