While all 27 pan-democratic lawmakers have pledged to veto any reform proposal based on the strict framework announced by Beijing last August, the diplomat sounded a note of optimism.

Arguing that it was in the city's best interests to accept the "imperfect" proposal, the diplomat, who spoke on condition of anonymity, believed a number of pan-democrats would change their positions before Legco voted on the proposal in June.

He said even under Beijing's restrictive framework, where only two or three candidates who secure support from the majority of a 1,200-strong nominating committee could run, the pan-democrats would still have a chance to field a candidate.

"If you have a very low entry threshold, the pan-democrat candidate could use opportunities such as televised debates to build a strong public backing. It would be politically very difficult for the nominating committee to veto somebody with such strong public support," he said.

The diplomat also said Beijing had recently been in contact with his mission to discuss the reforms. "I don't think Beijing is indifferent ... But in a sense, they are saying 'that's the best we can do, at least for now'," he said.

Meanwhile, in a sign of disunity in the pan-democratic camp, Civic Party lawmaker Ronny Tong Ka-wah said he was "tired" of joint pan-democratic petitions against the reform proposal under Beijing's framework and would not sign any more.

He said he would vote down the plan unless the central government made the concessions that would win the pan-democrats' support.

Tensions are expected to heighten on Saturday as officials kick-start the latest publicity drive in the community to garner support for Beijing's plan.

National People's Congress deputy Andrew Yao Cho-fai yesterday said he understood that the pro-establishment camp would launch two rounds of campaigns, in May and June, to collect signatures from residents who wanted lawmakers to approve the reform package.