BEIJING (Reuters) - He Lifeng, head of China's state planning agency, is likely to succeed the country's economic tsar Vice Premier Liu He in March, but may struggle to maintain his predecessor's policy clout.

He, 67, a confidant of President Xi Jinping, was elevated to the ruling Communist Party's Politburo during its once-every-five-years congress this month. That paves the way for He's expected promotion as the 70-year-old Liu is due to step down in March.

The top priority for He will be to help Li Qiang - another Xi ally, tipped to become the new Premier in March - to pull the world's second-largest economy out of its worst downturn in decades amid disruptive COVID-19 curbs and a prolonged property crisis.

The departing Liu, Xi's top economic adviser and a childhood friend, holds an unusually powerful portfolio: it covers economic policy, the financial sector and trade ties with Washington, overshadowing the role of outgoing Premier Li Keqiang.

Xi, who secured a precedent-breaking third term as president at the party conclave, may want to restore some of the premiership's previous power under the incoming Li Qiang. Some analysts say part of the expanded role that Liu built up during his time as economic tsar could be taken over by other top officials.

Related video: Goldman's Hui Shan on China's Growth