A senior Nippon Steel executive said he would meet the United Steelworkers (USW) union chief this month to seek support for acquiring U.S. Steel, expressing confidence the deal can be finalized by the end of September.

Gaining their backing could help the world's fourth-largest steelmaker carry the $14.9 billion purchase of its U.S. rival over the line. The merger has drawn criticism from some Democratic and Republican lawmakers who worry about the national security implications of the takeover — even though the U.S. and Japan are close allies — and the powerful USW, who worry how their workers could fare under Nippon Steel's management.

"I think we've cleared the contractual issues," Executive Vice President Takahiro Mori said in an interview on Wednesday, emphasizing Nippon Steel's plan to uphold all of the current agreements between the union and U.S. Steel.