JPMorgan Chase ($54.11 0.26%) opposed Lehman Brothers Holdings Inc.’s bid to pull Bruno Iksil, known as the “London Whale” trader, into an $8.6 billion fight between the biggest U.S. bank and the defunct investment bank.

Lehman asked a bankruptcy judge this month to let it try to force Iksil to testify on valuations of derivatives trades in 2008 that Lehman said spurred unnecessary margin calls and hastened its bankruptcy.