UNITED NATIONS, SEPT. 18 -- U.N. Secretary General Javier Perez de Cuellar pleaded today for authority and funds to organize a standby peace-keeping operation, warning that the world body is stretched to the limit in money and manpower.

In his annual state-of-the-world report, issued hours before the 45th session of the General Assembly opened today, Perez de Cuellar declared, "We have funds for only 24 further days of operation." He cited a debt of over $1 billion in regular dues and peace-keeping contributions, of which the United States owes about half.

He said the United Nations has launched 18 peace-keeping operations since 1948, five of them in the last three years, and faces the possibility of intervening in Cambodia, El Salvador and Western Sahara.

"We are being asked to do more with fewer resources and even those are sometimes provided too late," he said. "The whole point is that we have reached a stage where limits to improvisation have come glaringly into view."

To this end he called for a reserve stock of basic equipment and supplies, the earmarking of military personnel and an increase in working capital as well as authority to set up an operation in advance.

"An operation . . . takes long planning and preparation," he said, "while the implementation of a settlement requires an urgency as soon as it is agreed upon."

In a review of world events, Perez de Cuellar said the Middle East continues to be the most explosive region of the world today: "Longstanding grievances which have festered for years have been aggravated by an escalating arms race throughout the area, which has spawned a deadly arsenal of weapons of mass destruction."

In Paris, the nine-nation Western European Union said it would ask the U.N. Security Council to extend the international trade embargo against Iraq to cover air traffic.

The council should "as soon as possible take extra measures for the complete and effective imposition of the embargo, including air traffic . . . . This should be applied, if necessary, to countries which do not respect the embargo," the group said.

French Foreign Minister Roland Dumas said a joint military committee would meet Wednesday to implement new steps to extend coordination of ground and air forces from WEU countries operating in the Persian Gulf.

The Netherlands said it would send a squadron of F-16 fighter-bombers to Turkey, which has a border with Iraq, to help enforce an air blockade if the United Nations decided to impose one.