The State Department has selected career diplomat A. Peter Burleigh to represent the United States in postwar Baghdad and career diplomat Raymond G.H. Seitz to be ambassador to Britain, sources said yesterday.

Burleigh, deputy chief of the department's Bureau of Intelligence and Research, is an expert on the Middle East and South Asia and has specialized in Persian Gulf matters for much of his 24-year career in the Foreign Service.

He would replace the current envoy, April C. Glaspie, who has been in Washington since shortly after Iraq's invasion of Kuwait. It is not clear what Glaspie's next assignment will be.

Glaspie, whose three-year tour in Baghdad would end this summer, was sharply criticized by some in Congress when, in accord with administration policy, she told Iraqi President Saddam Hussein shortly before the Aug. 2 invasion of Kuwait that the United States would take no position on Iraq's border dispute with Kuwait.

Despite the war, the United States has not broken relations with Iraq, and the U.S. Embassy, while vacant, is not technically closed. The last U.S. diplomats left Baghdad in the week before the war started.

According to a senior administration official, the 48-year-old Burleigh is part of a group chosen for ambassadorial posts mostly in June when the State Department deputies committee looked at about three dozen slots due for rotation under the three-year policy. Glaspie, the official said, "is not due for a new assignment" in another embassy.

Most of the three dozen are in the process of clearance in preparation for sending their names to the Senate for confirmation.

Seitz would be the first career Foreign Service officer to get the prestigious posting to the Court of St. James's.

The 50-year-old Seitz, who is assistant secretary of state for European and Canadian affairs, has served in London twice before, once in 1975 and again from 1984 to 1989 when he was the deputy chief of mission. Seitz also has served in Canada, Kenya and Zaire.

The largest rotation of envoys is due in 1992, with some 70 ambassadors, most of them political appointees named in the first year of the Bush administration, scheduled to leave their posts.

"They were told at the outset that this would be a three-year deal and they would be replaced by another group of political appointees," one official said, adding that many "want to believe" they will be able to stay longer.

The administration, however, is considering leaving the political appointees in that group in place until after the 1992 reelection campaign.

The State Department wants to replace Jack F. Matlock Jr., the ambassador to the Soviet Union, who is nearing the end of his fourth year, one year beyond his regular rotation. Officials said State "took a stab at it last year for his sake, not because there was any dissatisfaction" with him. The effort "didn't jell," an official said, and a new list of possible replacements is being organized.

The administration has not decided what to do about two other nominees whose confirmations were blocked last year by Sen. Jesse Helms (R-N.C.), the ranking minority member of the Senate Foreign Relations Committee.

Some administration officials considered nominating John Bushnell, who had been tapped earlier to serve in Costa Rica, for the Dominican Republic. But according to administration officials, Helms sent back word that he "will be held up for any diplomatic post anywhere in the world." The same was said to be the case for George Fleming Jones, who had been nominated to be ambassador to Guyana.

Officials said they are holding out the Seychelles for a political appointment and there are several candidates, none yet selected. Among other countries expected to get new ambassadors are Algeria, Bolivia, Chile, Colombia, Egypt, El Salvador, Equatorial Guinea, Israel, Malawi, Mauritania, Niger, Pakistan, the Philippines, Paraguay, Senegal, Syria, Uganda, Dominican Republic, Thailand and Tunisia.

Meanwhile, at the Soviet Foreign Ministry in Moscow, names are floating around to replace the Soviet ambassador to Washington, Alexander Bessmertnykh, who has replaced Eduard Shevardnadze as foreign minister.

The most often-mentioned are a group of usual suspects for such a high-ranking post. The group, according to a senior Soviet official, includes U.N. Ambassador Yuli Vorontsov, Deputy Foreign Minister Vladimir Petrovsky and Alexander Belonogov, who replaced Bessmertnykh in Moscow as deputy foreign minister for American affairs when Bessmertnykh came to Washington last year.