China's rubber-stamp lawmakers tonight passed a historic constitutional amendment abolishing presidential term limits that will enable President Xi Jinping to rule indefinitely.

The National People's Congress' nearly 3,000 hand-picked delegates endorsed the constitutional amendment, voting 2,958 in favour with two opposed, three abstaining and one vote invalidated.

The amendment upends a system enacted by former Chinese leader Deng Xiaoping in 1982 to prevent a return to the bloody excesses of a lifelong dictatorship typified by Mao Zedong's chaotic 1966-1976 Cultural Revolution.

The slide toward one-man rule under Xi has fueled concern that Beijing is eroding efforts to guard against the excesses of autocratic leadership and make economic regulation more stable and predictable.

In a sign of the issue's sensitivity, the government censors are aggressively scrubbing social media of expressions ranging from "I disagree" to "Xi Zedong."

US President Donald Trump was criticised last week for seeming to approve of Xi's unlimited rule, saying: "President for life... I think it's great. Maybe we'll have to give that a shot someday."