Beijing's top man in Hong Kong has dropped the clearest hint yet that a screening mechanism could play a role in selecting future chief executives.
Zhang Xiaoming, director of the central government's liaison office in Hong Kong, also said that national sovereignty and security must be protected as the city achieves universal suffrage by 2017.
During a lunch with 50 lawmakers on his unprecedented visit to the Legislative Council, described by one as "cordial on the surface", Zhang delivered strong messages in a friendly and sometimes jocular tone. But outside the building later he took a tougher line, slamming the Occupy Central civil disobedience campaign, which he said would be a disaster with "lasting consequences" for Hong Kong.
He told lawmakers: "There is no doubt of the central government's position - and sincerity - to support Hong Kong achieving universal suffrage.
"[But] the methods must follow the actual situation of Hong Kong, which means it is not a country. It is by no means an unreasonable demand that national sovereignty, national safety and the rights of the central government must be well protected."
Radical lawmakers were on their best behaviour - there were no objects thrown or slogans chanted. "Long Hair" Leung Kwok-hung gave Zhang a book on the Communist Party's pledge for democracy during its struggle against the Kuomintang in the 1940s, while People Power's Albert Chan Wai-yip and Raymond Chan Chi-chuen offered another book entitled Don't Want to be a Chinese in My Next Life.
The three then left the dining hall after presenting their gifts.
Zhang used another gift - a sieve given by lawmaker Frederick Fung Kin-kee - as a metaphor to illustrate the advantages of a screening process. "What is the sin of a sieve?" he asked. "It was our ancestors' wisdom that invented the sieve. Otherwise how can we sift fine grains from coarse grains? We cannot simply deny that a sieve has its function."
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Labour Party lawmaker Lee Cheuk-yan said the meeting was "cordial on the surface" but there was "a lot of tough talk" on universal suffrage. "The hint of a screening process also touches a nerve as it gives a very bad message that universal suffrage in 2017 will not be a genuine one that reflects the people's will," Lee said.
Civic Party leader Alan Leong Kah-kit believed Zhang was not serious with his metaphor.
"The most effective sieve would be one that let millions of voters sift the candidates that they do not prefer," he said.
Beijing-loyalist Tam Yiu-chung, chairman of the Democratic Alliance for the Betterment and Progress of Hong Kong, played down the metaphor. "I do not think it has anything to do with electoral reform," he said.
Nineteen of the 27 pan-democratic lawmakers attended, while Zhang brought 11 colleagues from the liaison office.