Nomura Holdings Inc.'s chief executive vowed to keep Japan's biggest brokerage independent and quickly implement his latest turnaround plan as a slumping share price puts the question of a potential merger in focus.

"We cherish the strengths and utility that we have through our independence as a Japanese financial group," CEO Koji Nagai said in an interview Friday in Tokyo. "It's not going to happen that we'll become part of a financial company elsewhere. We're not thinking about such a thing."

Nagai, 60, unveiled plans this month to cut $1 billion worth of expenses from Nomura's struggling global trading and investment banking business, a move that has already resulted in dozens of job cuts worldwide. The firm's valuation is close to the biggest discount to global peers in two decades, as investors digest whether the restructuring plan will end years of overseas losses since it bought Lehman Brothers Holdings Inc. operations in 2008.