DUESSELDORF, Germany (Reuters) – Labour leaders, who hold half the seats on Thyssenkrupp’s supervisory board, will not support a planned joint venture with Tata Steel if concessions in ongoing antitrust proceedings go too far, a union representative said.

“We won’t support a merger at any price,” Markus Grolms, vice chairman of Thyssenkrupp’s supervisory board and secretary at IG Metall, Germany’s biggest labour union, told Reuters.

Thyssenkrupp and Tata Steel are planning to combine their European steel activities to create the continent’s No. 2 steelmaker after ArcelorMittal, raising concerns that far-reaching remedies are required to secure antitrust approval.

The European Commission is expected to sent a so-called statement of objections this week in which it will outline areas of particular competitive concerns, forcing the companies to come up with remedy ideas to avoid a potential veto.

“We have always defined a red line with regard to the merger control proceedings. If this line is crossed we won’t give our support,” Grolms said, without saying where the line would be drawn.

Thyssenkrupp Chief Executive Guido Kerkhoff a day earlier said the Commission’s statement, expected at the end of the week, was not unusual given the transaction’s size and gave no reason for fresh concerns.

The steel-to-submarines group is still confident it can complete the deal in early 2019. The European Commission will rule on the transaction by April 29.