Steelworkers at German industrial giant ThyssenKrupp have won guarantees that their jobs are secure until 2026, bringing the group a step closer to its planned merger with India's Tata Steel.

ThyssenKrupp said late Thursday it had clinched a deal with Germany's powerful IG Metall union pledging there would be no job losses or major site closures until September 2026.

"The outcome achieved today represents a key prerequisite for meeting our strategic objectives and at the same time satisfying the interests of our employees," ThyssenKrupp CEO Heinrich Hiesinger said in a statement.

The agreement, which still needs to be approved by union members, clears a major hurdle for the conglomerate as it seeks to combine its steel operations with Tata to create Europe's second biggest steelmaker after ArcelorMittal.

ThyssenKrupp and Tata say the tie-up is necessary to combat chronic overcapacity in an industry roiled by a flood of subsidised Chinese steel.

While the merger will allow for economies of scale and other savings, the firms have warned it will also lead to some 4,000 job cuts that will be shared roughly evenly between the two groups.

ThyssenKrupp, which makes products ranging from car parts to elevators to submarines, has said it is not planning any forced redundancies.

Turning to its German steel works, it said "the future of the majority" of the sites was assured for the next nine years under the deal.

But the group said it would only guarantee operations for the sites in Bochum, Eichen and Huettenheim in western Germany until 2021.

ThyssenKrupp also promised to invest "at least" 400 million euros ($470 million) a year in its German steel works and retain the voting rights of German workers' representatives on the new supervisory board.

The merged holding company, to go by the name Thyssenkrupp Tata Steel, will be headquartered in the Netherlands.

It will have combined annual sales of some 15 billion euros and employ 48,000 people across 34 sites.

The tie-up should be completed by the end of 2018, added the German group.