China's president-in-waiting Xi Jinping has praised his predecessor Hu Jintao for voluntarily stepping down from both his party and military posts, promising to uphold his legacy of defence modernisation, state media said on Saturday.

Hu, who remains China's president until March's parliament session, relinquished the much more powerful post of Communist Party boss on Thursday. Jinping on Saturday formally took over as the country's military chief, presiding over the first meeting of the powerful 11-member Military Commission, the highest body of the country's defence command structure.

The question had loomed whether Hu would stay on as head of the powerful Central Military Commission.

Hu's predecessor Jiang Zemin remained chief of the military commission for two years after Hu took over as president and party boss.

"Chairman Hu, giving full consideration to the development of the party, country and military, voluntarily proposed no longer holding the positions of party general secretary or chairman of the military commission," the official Xinhua news agency cited Xi as saying. "The entire 18th Party Congress respected Chairman Hu's willingness (to step down), and agreed to his request."