ArcelorMittal had said in May that it would halt for some time the plant in Krakow, southern Poland, in September, due to rising carbon emission costs and surging power prices.

"We have decided to postpone the idling of primary operations in Krakow, originally planned for September as we want to reevaluate the whole situation," ArcelorMittal said in a statement.

The steel maker, which employs more than 11,000 people in Poland, said in May that the decision to shut the blast furnace and steel plant would affect 1,200 people, who would be transferred to other jobs or granted idle-time pay.

"We would like to once again underline that the idling will be temporary and that none of our employees will lose their job during this standstill. We are committed to our presence in Poland and want to continue to produce steel here," ArcelorMittal said in the Thursday statement.

A Polish state-run news agency said around 1,000 trade union members protested on Wednesday in front of ArcelorMittal's local headquarters in Dabrowa Gornicza, also in southern Poland.

(Reporting by Agnieszka Barteczko; Editing by Dale Hudson)