Kakao Pay Corp., the fintech unit of South Korean tech giant Kakao, said Thursday it plans to acquire a controlling stake in Siebert Financial Corp., a US brokerage firm, as part of efforts to expand its financial business abroad.

Kakao Pay said in a regulatory filing it has signed a deal to purchase Siebert's new shares worth $17 million.

The deal, set to be completed on May 4, will allow Kakao to secure a 19.9 percent stake in the New York-based firm.

After winning approval from shareholders and US regulators, Kakao Pay will also buy an additional 31.1 percent stake next year, subject to shareholder and regulatory approval, eventually holding 51 percent of the shares.

Kakao declined to provide terms of the second batch of the deal.

"Kakao Pay has attained a great opportunity to expand its financial business abroad by making a strategic investment in Siebert, a company with over 55 years of tradition and experience," Kakao Pay CEO Shin Won-keun said in a press release.

"We will continue to enhance our user experience and benefits as a financial platform, and seek new chances for innovation in the global market."

Kakao Pay, which also operates a stock trading platform, is expected to enhance its services for trading overseas shares on the back of the acquisition.

Listed on the tech-heavy Nasdaq, Siebert provides various brokerage and financial advisory services, including securities brokerage, investment advisory and insurance offerings.

Shares of Kakao Pay closed at 56,200 won ($41.9) on the main bourse Kospi Thursday, up 3.69 percent from the previous day. The report was released after the market closed. (Yonhap)