NEW YORK (Reuters) - Jefferies Financial Group ( JEF ) said on Monday that Japan's Sumitomo Mitsui Banking Corp (SMBC) has more than doubled its stake in the U.S. investment bank to 10.9%, deepening an alliance dating back to 2021.

As part of the expanded ties, Toru Nakashima, the CEO of Sumitomo Mitsui Financial Group ( SMFG ), SMBC's parent, joined Jefferies' board of directors on Monday, the U.S. bank said in a statement.

SMBC plans to increase its ownership of Jefferies to as much as 15%, as flagged last year.

Under the partnership, Jefferies dealmakers take the lead on mergers and acquisitions (M&A) and equity capital markets (ECM), while SMBC bankers focus on corporate lending and investment-grade debt issuance.

"There's an active and broad pipeline of M&A, ECM and leveraged financing activities involving SMBC and Jefferies working together," Jefferies President Brian Friedman told Reuters. "There's been a good number of completed deals and more in the pipeline."

SMBC's hefty balance sheet and its international client roster have boosted Jefferies' involvement in overseas deals.

"In the few short years that our strategic alliance has existed, it has already borne meaningful opportunities," Nakashima said in the statement.