HONG KONG — Backing down after days of huge street protests, Hong Kong’s chief executive, Carrie Lam, said on Saturday that she would indefinitely suspend a bill that would allow extraditions to mainland China.

It was a remarkable reversal for Mrs. Lam, the leader installed by Beijing in 2017, who had vowed to ensure the bill’s approval and tried to get it passed on an unusually short timetable, even as hundreds of thousands demonstrated against it this past week.

But she made it clear that the bill was being delayed, not withdrawn outright, as protesters have demanded.

“I believe that we cannot withdraw this bill, or else society will say that this bill was groundless,” Mrs. Lam said at a news conference.