Last-ditch talks agreed between the Hong Kong government and student protesters may have temporarily relieved tensions -- but what can the authorities really offer pro-democracy campaigners? And would Beijing ever agree to significant concessions?

The city has seen nearly a week of mass demonstrations and although numbers have started to dwindle after a two-day public holiday, some are not ready to go home.

Thousands crowded outside the central government offices on Thursday ahead of a midnight deadline for Chief Executive Leung Chun-ying to resign. Leung's offer just before then of talks defused a potentially explosive standoff between protesters and police.

But even as Leung spoke of his plan for Chief Secretary Carrie Lam to enter discussions with the Hong Kong Federation of Students (HKFS), there was scepticism over what dialogue can achieve.

"What the people want is a concrete reply on what the government can offer us," student leader Yvonne Leung told AFP.

- Strict parameters -

Beijing says only candidates vetted by a loyalist committee will be allowed to stand for Hong Kong's leadership elections in 2017, a decision dismissed as "fake democracy" by activists who want candidates to be nominated by the public at large.

China says the nominating committee would be similar to the 1,200-strong group of pro-Beijing worthies that currently appoints the chief executive.

Analysts believe that Beijing is highly unlikely to budge from that framework, laid down in August.

"Beijing already set out the legal and political bottom line... and negotiations have to adhere to those parameters," said political analyst Sonny Lo at the Hong Kong Institute of Education.

"The government has now decided on dialogue, which is good, but the students may need some tactical mediators. They have to understand the Chinese style of negotiation.

"It's not that they have to completely let go of the idea of civic nomination (of candidates by the public), but they have to think of some other tactic, like a civic recommendation that is put forward to the nominating committee," says Lo.

- 'Cosmetic concessions' -

Others feel that any concessions that are granted will ultimately be meaningless.

"Beijing may be agreeable to cosmetic change, but it would have no impact," said Willy Lam, a China scholar at the Chinese University of Hong Kong.

"It would be a face-saving measure to give the appearance that Beijing is making concessions, but it would be 100 percent unacceptable to student leaders and the leaders of Occupy Central."

Analysts say that this would leave the campaigners with no option but to continue their civil disobedience campaign -- but that risks alienating the public, who have so far been largely supportive.

"It's like a poker game," said Lam. "It depends on whether they can still call tens of thousands onto the street. The support of the Hong Kong public is crucial to the protest movement."

- Divide and conquer? -

Student group HKFS is the only organisation set for talks with the government, after it sent an open letter to Carrie Lam. But the protest movement is made up of a range of groups including Occupy Central (a cross-section of society), Scholarism (students) and some lawmakers.

Some analysts believe that this may be a calculated move by Leung to "divide and conquer" the broad-based democratic group.

"The protesters' weak link is that there is no unified command," said Lam.

While he described HKFS as a "radical group", their letter -- which dropped the demand for Leung to resign -- showed signs of compromise.

Lam said Leung would now go after the support of moderates within the movement.

"He is trying to reach the so-called 'soft democrats'" who might accept low-level concessions that the students would not, says Lam.

- Leung won't go -

While protesters portray Leung as a Beijing stooge, analysts say he is part of the ruling machine and will be given a free hand to act as he sees fit, within the parameters laid down by China.

"C.Y. is not a puppet of Beijing, he is part of the leadership of China and is a trusted hand with direct contact," said local councillor Paul Zimmerman.

Some analysts say Leung has become a liability to Beijing and may eventually be put out to pasture, but they agree that there is little prospect of that happening soon.

A game changer could be if the demonstrations in Hong Kong start to have a significant impact on the mainland -- where news of the protests has been tightly controlled -- and if President Xi Jinping comes under increasing fire from critics in his own party as the crisis stretches on.

"If news starts to (cause) unrest in China and political activism on that side... then there will be more and more pressure to take action," said Zimmerman.