Striking dockers vowed action with the effect of a "nuclear bomb" if talks with contractors in the dispute over their pay and conditions break down today.
The threat came as a government source said the administration had set an objective of settling the dispute this week.
No details were given of the planned action, but there were suggestions that the Cheung Kong Center in Central, headquarters of Asia's richest man Li Ka-shing, had been considered as a target.
A source with knowledge of the strikers' planning said the organiser, the Confederation of Trade Unions, had two to three plans and would immediately go ahead with one today if talks with contractors Everbest Port Services and Global Stevedoring Service failed.
Strike organiser Stanley Ho Wai-hong would say only that the action would be in the form of a sit-in. But he added: "The actions we have planned will be like a nuclear bomb."
Another source said the action would have an impact on the entire logistics industry and even society as a whole.
"We have gathered the support of more dock workers working for other contractors in our next actions," the source said.
"It has come to a stage where they think it is time to come out."
The action would be aimed particularly at one individual, the source said, without saying who that would be or how many additional people would join the 450 striking dockers.
The source said the organiser had considered occupying the Cheung Kong Center in Central, but did not say if this was a firm plan. Li's Hutchison Whampoa is the parent company of the strike-hit port operator Hongkong International Terminals (HIT).
Ho said after a closed-door meeting with the strikers on the 19th day of the strike yesterday that they would not step up their actions if the contractors showed "sincerity" at today's meeting.
He said a 7 per cent raise proposed by the contractors last Thursday was definitely not sincere enough. The dockers are demanding HK$100 more per shift, up about 20 per cent.
The confederation will meet the contractors this afternoon with a representative of HIT attending as an observer. There will be another meeting for the two contractors, HIT and two other union groups who so far have not joined the strike - the Federation of Trade Unions and the Federation of Hong Kong and Kowloon Labour Unions.
The Union of Hong Kong Dockers said the strike fund had raised HK$5 million by yesterday and would be enough to subsidise strikers for the next nine days. It handed out HK$1,500 each to workers yesterday.
Federation of Hong Kong and Kowloon Labour Unions chairwoman Ng Wai-yee said her union also had plans for escalation if the pay rise was refused.