New York City is poised to mandate that thousands of companies provide paid time off for sick employees, bolstering a national movement that has been resisted by wary business leaders.

A legislative compromise reached on Thursday night represents a raw display of political muscle by a coalition of labour unions and liberal activists who overcame fierce objections from New York?s business-minded mayor, Michael R. Bloomberg, and his allies in the corporate world.

The deal required a high-profile concession from a leading candidate to succeed Mr. Bloomberg, Christine C. Quinn, the City Council speaker, who had single-handedly blocked action on the sick-leave issue for three years, arguing that it would inflict damage on the city?s fragile economy.

The legislation would eventually force companies with at least 15 employees to give full-time workers five compensated days off a year when they are ill, a requirement that advocates said would allow much of the city?s labour force to stay home from work without fear of losing a day?s wage ? or worse, a job. The advocates said the legislation would provide paid sick leave for one million New Yorkers who do not currently have such benefits. But to the disappointment of those who pushed for a more sweeping version of the legislation, New York City?s mandate would not take effect until spring 2014, and for the first 18 months, it would apply only to businesses with 20 or more employees, according to people involved in the negotiations.The measure is subject to a vote by the City Council. Mr. Bloomberg is expected to veto the measure, but there is enough support on the Council to override his veto.