China's reported choice for Hong Kong's next leader promised Monday to "set the stage" for universal suffrage, as he held a rally ahead of March polls expected to be heavily influenced by Beijing.

The wealthy businessman and former Number Two in the southern financial centre unveiled the campaign slogan "We Are Tomorrow" at a tightly scripted rally before around 2,000 supporters in the harbour side convention centre.

He made vague promises to tackle inequality and social tensions in a city that boasts Asia's widest wealth gap, including more public housing and higher education spending "as a prerequisite for mitigating poverty".

"I will do my best to raise the quality of life for the middle class and enhance their potential for social mobility," he said, promising to "enable every citizen to live in dignity".

The 59-year-old former chief secretary has the backing of business and finance leaders in the city of seven million people, a former British colony that has boomed as a gateway to China since its 1997 handover to Beijing.

The March 25 election will be in the form of a vote by a 1,200-member electoral committee packed with Beijing-backed appointments and members of the business elite.

Current Chief Executive Donald Tsang's term ends in June and he is unable to run again.

Tang is believed to have the support of most committee members and the quiet backing of the central government in China.

His main rival, former cabinet member Lung Chun-hing, 57, is well ahead in public opinion polls but is seen as an outside chance of winning the votes he needs in the electoral committee.

The next chief executive will serve a five-year term until 2017 when full suffrage is expected to be introduced, as long as Beijing approves.

Tang pledged to "make history" in 2017 with a chief executive election on a one-man-one-vote basis.

"We will set the stage for delivering universal suffrage and ensure the process will be fair, just and open," he said.

"At the same time we will groom democratically elected political talent for the future."

Tang's campaign got off to a shaky start after he publicly admitted cheating on his wife, but analysts say his infidelities are unlikely to hurt his election chances.