The Japanese parliament today appointed Yasuhiro Nakasone, a 64-year-old conservative politician with a populist flair, Japan's 16th prime minister since World War II.

Nakasone, who Wednesday won a landslide victory for president of the ruling Liberal Democratic Party, succeeds Zenko Suzuki as head of the business-oriented, largely pro-American government here. He has pledged to strengthen ties with the United States, which have been strained as a result of Japan's cautious approach in dealing with the thorny issues of trade and defense.

"Should relations with the United States be shaken, no other policies will work effectively," Nakasone told reporters after being named LDP president at a party convention yesterday. Known for his hawkish views, he indicated he may favor the revision of Japan's war-renouncing constitution, which was put in place by U.S. occupation forces after World War II.

But Nakasone is unlikely to make any dramatic changes in Japan's defense or economic policies, according to political analysts here. His stronger grasp of global issues, however, may help improve ties with the United States that he called "the crux of Japan's foreign policy," according to the analysts.

The United States, suffering a huge trade deficit with Japan, has called on the country to quickly open its markets to more American goods and has asked Tokyo to accelerate its defense spending to offset the burden of American military commitments in the Pacific.

At a press conference yesterday, Nakasone vowed to more clearly define policies on key issues facing the nation so that they might be more easily understood by the general public. In Japan's strongly consenus-seeking society, policy decisions are often achieved by negotiations among the country's powerful political and business leaders and its elite career bureaucrats far from public view.

Nakasone indicated that he would make greater use of television to "bring national politics into the living-rooms" of Japan, something his predecessors avoided.

Nakasone told reporters that he would give top priority to cutting out the fat in government to help reduce Tokyo's massive public deficits. He said, however, that his predecessor's target of balancing the national budget by 1984 would no longer be possible and promised to hold the line against tax increases.