By Fabian Cambero

SANTIAGO (Reuters) - Unionized workers at BHP Billiton Plc's (BHP.AX)(BLT.L) Escondida copper mine in Chile, the world's largest, ended a 24-hour strike on Friday but could put down their tools again next week over the company's planned layoffs, the union said.

Workers resumed their activities at the mine without incident at 8 a.m. local time (1100 GMT), union official Carlos Allendes told Reuters. Workers plan to strike again on Wednesday unless the company reverses its plan to fire workers, he added.

BHP said this week it has decided to lay off 120 workers, or approximately 3 percent of the mine's workforce, amid adjustments to its operations.

BHP did not respond to requests for comment.

The union said the layoffs are a reprisal for a lengthy strike in the first quarter and an attempt to intimidate workers ahead of pending negotiations over new labour contracts.

The union at Escondida ended a more than 40-day strike in March by temporarily extending its old contract by 18 months, pushing forward a new round of talks to 2018.

Chile is the world's biggest copper exporter.

On Friday, a pro-union group of protesters showed its support for workers by demonstrating in front of the mine's port of Coloso, a union spokesperson said.

(Reporting by Fabian Cambero; Writing by Mitra Taj; Editing by Jeffrey Benkoe)