BALTIMORE -- A former currency trader accused of hiding $691 million in losses pleaded guilty Thursday in one of the biggest bank fraud cases in U.S. history and will get 7 1/2 years in prison.

Prosecutors said John Rusnak fabricated trades to cover the losses and make it appear as if Allfirst bank was making money. That, in turn, enabled him to collect big bonuses.

"It's a bitter pill," defense attorney David Irwin said. "It's a lot of time."

He will be sentenced in January, receiving a prison term worked out in a plea bargain. As part of the deal, the 37-year-old father of two also agreed to cooperate with investigators in the continuing probe.

"Mr. Rusnak undertook a sustained and concentrated effort to avoid the bank's accountability system, and whether he had help in that at this time has not been determined," U.S. Attorney Thomas DiBiagio said.

Rusnak was indicted in June in the biggest bank fraud case since Nick Leeson lost more than $1 billion on futures trades and caused the 1995 collapse of England's distinguished Barings Bank.

Rusnak ran up the losses at Allfirst Financial over five years, mostly from trading Japanese yen. Prosecutors said Rusnak did not directly profit from the trading losses, but by manipulating Allfirst's computerized system of tracking trades, he was able to make it look as if the bank was making money instead of losing it.