Formal talks between the Hong Kong government and students are set for the end of this week but pro-democracy protesters said Wednesday they were sceptical over what the negotiations would achieve.

While numbers at demonstration sites around the city have dwindled to a few hundred after days of mass rallies to demand fully free elections, those who remain at the barricades say they will not give ground.

"This is an important spot -- we should hold on to this regardless of how many people we have," said Helix Kwok, an 18-year-old student who was among a dozen protesters camping outside the Chief Executive's office Wednesday.

"If we withdraw, the government will then ignore us. With us here, we can react to anything that happens."

The government complex has been one of the key protest sites and scene of tense standoffs between police and students, with Wednesday's opening of parliament called off over security fears.

Protesters are demanding "true democracy" after Beijing insisted that it vet candidates for the city's 2017 leadership elections.

Rising social inequality, the soaring cost of living and distrust of the government is also fuelling discontent, particularly among Hong Kong's disillusioned youth.

After three rounds of "preparatory talks", formal talks are now set for Friday afternoon between students and Chief Secretary Carrie Lam -- the deputy to Hong Kong's embattled leader Leung Chun-ying.

Pro-democracy organisers had agreed to talks earlier with Lam but called them off last Friday after what they described as "organised attacks" on protesters at the Mong Kok demonstration site.

Student leader Lester Shum said the movement was keen to enter into talks -- but voiced concern over underhand tactics.

"We urge Hong Kong officials and Carrie Lam to face the problem of political reform directly, not to use tricks to play us again," he told reporters late Tuesday night after the date for dialogue was announced by the government.

Those on the streets Wednesday were also reticent over the government's intentions.

"I'm not very hopeful about the outcome," said Timothy Sun, 17, who has spent 10 days at the main Admiralty protest site.

"I think the government is going to repeat the same thing as before -- instead of accepting our requests such as civil nomination, they say that we'll have free elections step-by-step, that sort of thing.

"I am going to stay on. I don't want this protest to be a failure."

Demonstrators are facing an increasing public backlash as road diversions due to the occupied sites continue to cause traffic gridlock.

But student leaders have made it clear that protesters will not move out completely until they have achieved their objectives.

The authorities have given no indication of concrete plans to clear the sites and reopen the roads.