"I'm a little sensitive about my age," said John J. McCloy, who turned 90 on Sunday. America's first civilian high commissioner for Germany was made an honorary citizen of Germany in ceremonies yesterday at the White House Rose Garden.

McCloy, who has also been president of the World Bank, chairman of Chase Manhattan Bank and the Ford Foundation and served the government under nine presidents, told President Reagan he was interested to note "compared to me, what a spring chicken you are."

Hale and fit, coatless and hatless despite a chill wind, McCloy reminisced briefly about his experience in two world wars (the second as assistant secretary of war), beginning with service under "a man who had fought Indians on the plains." America he called "a young country . . . its great destinies are ahead of it." And the German people, in particular the Berliners, he praised for their "civil courage, spirit and strength."

West German President Richard von Weizsacker cited McCloy's work in helping Germany recover from World War II and Nazism to become "one of the free and prosperous countries in the world, which was by no means to be foreseen in the early postwar period."

He especially remarked on McCloy's "human decency in helping the beaten enemy to recover" and his trust in the democratic roots of the German people.

McCloy's term of duty in Germany came during the tense days of the Soviet blockade and the famed Berlin airlift. He also took part, as President Reagan noted, in "30 years of disarmament negotiations." The president spoke of McCloy's "selfish heart," amending that with some emphasis to "selfless."

The mayor of Berlin, Eberhard Diepgen, presented a plaque awarding McCloy "the highest distinction that free Berlin can give." He too spoke of how McCloy "helped us to rebuild a country which had been destroyed," mentioning the American Memorial Library that McCloy helped establish, as well as the Free University and the Aspen Institute of Berlin.

McCloy, who was also honored yesterday at a lunch sponsored by the American Council on Germany and hosted by Sen. Charles McC. Mathias (R-Md.), appeared to be in fine fettle. He had the last word about his age: "A friend of mine -- I'm sure he was a friend -- once said to me, 'Jack, did you ever stop to think . . . in a few years your life will represent one-half the life of the entire country . . .' "