March 20, 1984

The United States warned Libya that there could be ''serious consequences'' if it interfered with the two Awacs surveillance planes that were sent to help deter Libyan air attacks on the Sudan, according to a Reagan Administration official. The Awacs were sent to Egypt to join Egyptian fighters in patrolling Sudanese airspace. (Page A1, Column 6.) Summit talks on the Common Market ran into problems when Prime Minister Margaret Thatcher of Britain again demanded far-reaching changes in the way the 10-nation European Economic Community works. A two-day meeting of European Government leaders in Brussels is widely seen as decisive for the trade-bloc's future and for Western Europe's hopes of closer economic and political unity. (A1:5.)

It was Walter F. Mondale calling. ''Is Mrs. Kuhn there?'' he asked. ''Mrs. Kuhn on other phone,'' replied Billy Kuhn, 3 years old. He hung up. The former Vice President was laughing when he called back. ''You've got a real professional operation there, Nancy,'' he said to Billy's mother.

The United States told Libya today that there could be ''serious consequences'' if it interfered with the Awacs surveillance planes that have been sent to help deter Libyan air attacks on the Sudan, an Administration official said. The State Department and the Defense Department confirmed that two Awacs planes, along with tanker planes, had been sent to Egypt to join Egyptian fighters in patrolling Sudanese airspace. Last Friday, a TU-22 bomber, said by the United States to belong to the Libyan Air Force, dropped five bombs on Omdurman, the Sudan's second largest city, and then returned to a base in the Kufra oasis of Libya. The target of the attack apparently was the Omdurman radio station, but the bombs missed, and hit other buildings, killing five people.

In the spring of 1981, a new management team at the Cherry Webb and Touraine stores in Pawtucket, R.I., met to grapple with the first annual loss in the long history of the specialty apparel chain. The chain is one of the biggest of its kind in the Northeast. And the four executives now and then glanced out of the window toward the company's distribution center one and a half miles away in South Attleboro, Mass. Most apparel chains put their main offices and distribution center in the same building, to improve communications and logistics. But for some reason lost in its history, CWT did not.

In rites of both majesty and whimsy, John J. O'Connor yesterday took occupancy of St. Patrick's cathedral chair as the eighth Archbishop of New York. ''Ich bin ein New Yorker,'' Archbishop O'Connor said, echoing President John F. Kennedy, who used German two decades ago to tell a West Berlin crowd, ''I am a Berliner.'' The archbishop drew one of many roars of applause from the congregation of more than 3,000 in the cathedral. Speaking decisively in a crisp voice, he also vowed to join a cooperative drive to overcome social ills such as hunger and to oppose abortion, and offered compassion to those who disagree with the church's views. Yesterday's ceremony completed the two-day installation of the Archbishop, which began Sunday afternoon as a formal service of canonical possession.