President Hafez Assad of Syria has launched an unusual personal campaign to blame American agents for increasingly open and violent opposition to his rule.

Arab analysts interpret Assad's intensive effort to focus attention on the United States as a sign the Syrian leader is becoming more alarmed about the widening scope of assassinations, strikes and popular unrest directed against his government.

Another sign of worry, they say, is the dispatch last week of several brigades of specially trained Army troops with tanks and armored cars to intimidate residents of Aleppo, a northern Syrian city that has been the scene of particular unrest. The deployment marked the second time since the beginning of the year that Army troops were sent to put down antigovernment agitation in Aleppo.

In that context, Lebanese and diplomatic sources here say the redeployment of some Syrian peacekeeping troops outside Beirut eastward toward the Syrian border reflects in part a desire in Damascus to have more units on hand for other interventions that might be necessary.

Previously, official Syrian explanations had centered on the underground Moslem Brotherhood as the main reason for the internal disorders, which have included several hit-and-run assassinations a week for the last year. These explanations alone have become insufficient, however, as the agitation has spread recently to encompass shopkeepers' strikes, demonstrations and street disorders in several Syrian cities.

In six speeches he has made recently, Assad specifically blamed the United States and its agents for the violence. Also included in his list of targets were Israel and Lebanon's Phalangist Party, the rightist Christian group with the largest organized militia. But the focus was Washington.

In a speech Sunday night to the Syrian Teacher's Syndicate in Damascus for instance, Assad said "American reaction" is fomenting the disorders through its operatives to weaken Syria and its opposition to the Camp David peace accords.

"The United States is the number one enemy of our people and our Arab nation," he said in a speech Tuesday. "What we are facing has been planned by the United States intelligence. It is America that sends, supplies and directs these agents. . . ."

Blaming "U.S. imperialism" has long been a reliable standby for Arab leaders seeking a scapegoat to explain their setbacks and stir popular indignation. Assad's string of personal appearances over the last week, however, marks a departure from the prudent style of leadership adopted by the former air force commander since he took over in a bloodless coup in November 1970.

His concentration on assigning blame to U.S. agents has revived concern for the safety of U.S. citizens in Syria. U.S. diplomats in Damascus are known to have expressed fears of an Iranian-style attack on the U.S. Embassy there last month.

At the time, they received assurances from Assad's government that nothing of the sort would be allowed to happen, sources said. But in his speeches last week, Assad announced plans to train and arm popular militias from among peasants and workers to fight his opponents, providing unwelcome reminders of Iran's Revolutionary Guards and armed student groups. u

Relations between the United States and Syria have soured considerably since the Camp David agreements of September 1978 and the Israeli-Egyptian peace treaty of a year ago. Under Assad's leadership, Syria has been in the forefront of Arab nations opposing Sadat and his new attitude toward Israel. f