Beijing (AFP) - China's propaganda machine kicked into overdrive Tuesday to defend the Communist Party's move to scrap term limits for President Xi Jinping as critics on social media again defied censorship attempts.

The country has shocked many observers by proposing a constitutional amendment to end the two-term limit for presidents, giving Xi a clear path to rule the world's second largest economy for life.

The rubber-stamp National People's Congress (NPC) is certain to endorse the move next week, meaning that Xi -- already China's most powerful leader in decades -- can stay as president beyond 2023.

Li Datong, a former editor at the state-run China Youth Daily, posted a draft letter urging legislators to vote against the move -- which would abolish term limits set in 1982 under Deng Xiaoping to prevent a return to the decades of chaos under Mao Zedong.

"It was the highest and most effective legal restriction meant to prevent autocracy or putting individuals above the party and the state," said the letter. It was not sent to legislators but shared with hundreds of people in a private group on China's WeChat phone messaging app.

"Lifting the term limits of national leaders will be ridiculed by civilised nations all over the world and also sow the seeds of chaos for China," said the text posted on Monday.

WeChat users trying to share screenshots of the letter saw their posts blocked.

Censors have scrambled to delete all dissenting comments on social media -- even the word "disagree" is blocked -- but users of the Twitter-like Weibo website kept speaking out Tuesday, two days after the party Central Committee announcement.

"So pathetic, we have 1.3 billion people, no one can resist," wrote one user.

Another lamented the lack of political reform: "I once believed that I could see a president elected by one man, one vote in my lifetime."

Scores of terms have been blocked, according to a list of dozens of words compiled by US-based internet tracker China Digital Times -- including "my emperor", "ascend the throne", "I oppose", "lifelong", and "Winnie the Pooh" -- the portly cartoon bear to which Xi has been compared.

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- 'Happier lives' -

The NPC, at its annual full session starting Monday, will also formally approve a second five-year presidential term for Xi, who is Communist Party chief and head of the armed forces in addition to being head of state.

Legislators will add his eponymous political philosophy to the state constitution.

State media defended the amendment in editorials that lavished praise on the communist party's overall leadership.

The English-language China Daily said the lifting of the presidential term limit "has been necessitated by the need to perfect the Party and the State leadership system".

The party has always proposed amendments that "have injected new ideas and concepts about where the country will go and how it will achieve its goal of rejuvenation and ensure people live happier lives," it said.

The Global Times, a nationalist tabloid, was even more profuse in its praise of the amendment in an editorial entitled "Constitution change responds to new era".

Since Xi took power, it wrote, "the new ruling team has not just been muddling along under the leadership of General Secretary Xi Jinping. Instead, it quickly started to deepen reforms in a comprehensive and magnificent way."

The newspaper took a shot at the political systems of the United States and Europe.

"It has shaped and affected quite a few Chinese people's mindsets. But some key parts of the Western value system are collapsing. Democracy, which has been explored and practised by Western societies for hundreds of years, is ulcerating," it said.

"China cannot stop and take a break... our country must not be disturbed by the outside world or lose our confidence as the West grows increasingly vigilant toward China."

The administration of President Donald Trump, who has called Xi a friend but regularly clashes with Beijing over trade, had a guarded reaction to the Communist Party's move.

"The president has talked about term limits in a number of capacities during the campaign and something that he supports here in the United States, but that's a decision that's up to China," said White House spokeswoman Sarah Sanders.