She was introduced to the game at age 8 by her grandfather, a tennis pro himself. At 15 she left home for a government-run tennis academy to be groomed for her career. In 1980 she was her country's national junior champion and a star on its international tours. In 1981 she became its top female tennis player.

Today Hu Na is on the sidelines, her racket temporarily laid aside, as she watches the match that could have the greatest effect on her life. The game is on the diplomatic court, and the 19-year-old tennis star from the People's Republic of China set the ball in play herself when she slipped away from her country's team during an international tennis tournament in California last July and requested political asylum in America.

Eight months later, there has been no final government word on her request, and the delay is taking its toll on the tall, round-faced tennis star, who granted a rare interview here last week during a brief trip from San Francisco where she has been living in self-imposed seclusion.

Since Hu's defection, Chinese officials have strenuously warned U.S. officials both publicly and privately that giving her political asylum would harm sporting exchanges and relations between the two countries. They repeated this concern to Secretary of State George P. Shultz on his trip to China last month, according to State Department sources.

Their sensitivity on the matter has led the Chinese to take the unusual steps of lobbying with U.S. Immigration and Naturalization Service officials and releasing emotional letters sent to Hu and Shultz by her parents, pleading for her return.

The State Department's Bureau of Human Rights, from whom INS normally seeks advice on political asylum decisions, gave INS a favorable recommendation for Hu's asylum several weeks ago, sources said. But so far INS, which has the final say, has not acted.

Hu, in Washington last week chiefly to meet with supporters on Capitol Hill, spent two hours discussing with a reporter her reasons for defection, her life in China and her plans if she is granted asylum here.

"Every day I think about my asylum case," she said, explaining through an interpreter that she made the decision to stay in the United States because she was being pressured to join the Chinese Communist Party.

Although joining the party would have assured her instant status and privileges in China, Hu said she resisted because her membership was being pushed by one particular faction within the party. As a well-known tennis player, Hu feared this faction would use her to help promote its political aims and that if the faction ever fell into disgrace, she and her tennis career would go with it.

Hu said that if she persisted in refusing to join the party, she "would be criticized as disloyal to the country and they would say I was anti the revolution." She might then be banned from playing tennis or sent to a labor camp or political "reform" school, she said.

Z.L. Yang, counselor at the Chinese consulate in San Francisco, denied that Hu was being pressured to join the Communist Party. "No one is pressured into the party. If one wants to join one has to apply and only when one goes through a strict selection process are you admitted into the party. It's not a party open to everybody," he said, adding that there was no truth to Hu's statement that she would be persecuted if she returned home.

Hu also said she had been criticized by local party and tennis officials for things such as straying from the group while on foreign tours, growing her black hair too long (it now falls well past her shoulders) and wearing tennis gear with American brand names that she purchased abroad.

During the interview in the home of one of her lawyers in Washington, Hu, a slender, 5-foot-8-inch woman who wore black corduroy pants, a black sweater and black boots, displayed a composed, low-key personality with a certain independent streak. She grew up in Chengdu, the capital of Sichuan province, in south central China. Her father is a basketball coach in the Chinese army and her mother, a former athlete, is a receptionist at a local sports organization. Both her grandfather and aunt played tennis.

From age 8 she attended a tennis camp after school each day, she said. Later, at the tennis academy, she trained an average of 7 hours a day. "In China whoever attends an athletic camp becomes a government employe, they get a wage and benefits," Hu said. She soon entered the tournament circuit, and eventually was allowed to travel abroad. Her first trip to the United States was in 1979.

Just before leaving for her fourth tour in the U.S. last year, Hu received another strong request to join the Communist Party when she returned. She said that while en route here, she deliberated the pros and cons of not returning home.

"I was not happy. I was sad because I knew I was going to be apart from my family," Hu said. "It's not easy to make this kind of decision."

"There really was no elaborate planning" for her defection, which took place July 20 in the middle of the 32-nation International Federation Cup Tournament in Santa Clara, Calif., said Hu's San Francisco lawyer, Edward C.Y. Lau. He said Hu contacted a Mandarin-speaking family she had met on a previous tour to the U.S. and told them she would like to stay. They found Lau.

Wearing warm-up pants and a short-sleeved sweater, she waited until her roommate was asleep on the prearranged night and at midnight walked out the side exit of the hotel to a waiting car. "I left the hotel without taking any personal stuff. I was very sad because I was missing my colleagues and concerned about missing the tournament the next day," Hu said.

She was taken to the home of a Chinese-speaking American family, where Lau met her for the first time that night. "She was very nervous, very cautious, she felt very tense," Lau said in the Washington interview. "It was difficult for me to get information out of her, it took quite a long time to break the ice."

Since then, Hu has been living in the San Francisco area with Chinese-speaking American families, mostly watching television and avoiding public places, including tennis courts, in order to avoid giving Chinese officials any opportunity to intercept her. "We figured the best security was to keep her in seclusion," Lau said.

Defections are a particularly delicate issue with the Chinese, who have found that they are an unwanted side effect of their move toward a more open policy on exchanges with the West. Hu is one of the most prominent of their cultural and sporting figures to defect.

Last week, without explaining why they opened a letter from Hu's parents to their daughter, the Chinese consulate in San Francisco released a copy of the letter along with two others to Shultz from Hu's parents and the Chinese Tennis Association, apparently in an attempt to induce Hu to voluntarily withdraw her asylum petition.

"Miss Hu Na is very young and does not speak any foreign language. Obviously she was inveigled to leave the team," the association wrote Shultz. Her parents accused "pro-Taiwan elements" for influencing their "young and inexperienced" daughter to leave China, an action that is "ruining our happy and harmonious family."

To their daughter, Hu's parents wrote that her failure to return home has "landed us in deep sorrows. Missing you, your mother has suffered many sleepless nights and wept numerous times. In short, your mother's health is failing, with each passing day. So if you still do not return to her side as you do now you could imagine what consequences would befall her."

Her parents also told Hu that since she left "the leadership has taken great care of us." Her mother was given a salary raise, and her brother, who also plays tennis, was approved for a job.

Despite her separation from her family, Hu said she still believes she made the right decision. If allowed to stay here, she said, her priorities will be going to school and learning English rather than entering the professional circuit because she feels insecure about her game and is not yet ready to go pro. "I like always to win the game," she said. "I don't like to lose, so according to my tennis skill now, I can't win a professional game. Maybe in the future if I improve my tennis then I could become a professional . . . I would like to go back to school first. I would play tennis for fun and practice."

Asked which American tennis players she would like to play against, Hu replied, "I like Martina's Navratilova volley form but I like the appearance of Chris Evert Lloyd . She's good-looking; she never shows her emotion. I am good at volleying, but my base line stroke is weakest. If I can volley like Martina and play the base line like Chris then I would be confident enough to play against them."