From 1977 to 1980, Oksenberg took a leave of absence from the University of Michigan to serve as a senior staff member on the National Security Council under the Carter administration, overseeing issues involving China and East Asia. Oksenberg encouraged the U.S. government to continue the Nixon policy of improving Sino-American relations by normalizing relations with China. That would be politically difficult since it would require the United States to allow a mutual defense treaty with Taiwan to expire. After an initial but less successful trip to Beijing in 1977 with Secretary of State Cyrus Vance, Oksenberg traveled with National Security Advisor Zbigniew Brzezinski to Beijing in early 1978, where they met with Leonard Woodcock, the head of the U.S. liaison office there, to lay the groundwork for establishing diplomatic ties between the two countries. On December 15, 1978, the United States announced that on January 1, 1979, it would recognize Beijing as the legitimate government in China, ending formal diplomatic relations with Taiwan, although the United States would still maintain informal ties with the island.