Allied Irish Banks has lashed out at Citibank's latest efforts to derail a $500m (€458m) lawsuit launched over a decade ago after rogue trader John Rusnak racked up $691m of losses at former AIB subsidiary Allfirst.
AIB claims that Citibank is relying on "illusory errors" to persuade a New York court that it should reconsider a June determination that denied, in part, Citibank's motion for summary judgment in the case.
Citibank wants the court to dismiss, "with prejudice", AIB's claims against it.
AIB sued Citibank, part of Citigroup, and Bank of America, after Mr Rusnak's losses came to light in 2002. Citibank was Allfirst's prime broker.
The Irish bank, now owned by the State, accused Citibank of furthering the fraud by engaging in Mr Rusnak's sham transactions.
Citibank has denied the allegations.
But In June, the judge hearing the case in the United States, said she believed there was "credible" evidence that Citibank misled AIB regarding Mr Rusnak's trades.
"Given how lucrative Rusnak's trading was to Citibank, it would not be far-fetched to infer that Citibank did so because it was motivated to keep Rusnak happy," she said.
But Citibank has insisted that the New York court has "overlooked undisputed facts and controlling law that compel dismissal of this action".
Part of its argument rests on whether or not Mr Rusnak was acting for his own personal gain, or to profit Allfirst.
AIB has claimed to the court that in attempting to secure either a summary judgment, or interlocutory appeal, Citibank is relying on arguments it made a number of years ago in court, and which were fully heard then and which were rejected at the time.
AIB, which wants the case to go to trial, also maintains that if the court grants an interlocutory appeal, that the final determination of that appeal is unlikely to be known before late 2016, or early 2017, further delaying a possible trial.
AIB has predicted that a trial would last between two and three weeks.
It said the case has involved extensive paperwork, including 680,000 documents, hundreds of hours of recorded telephone calls, more than 100 fact depositions in three continents and 15 expert reports.
Bank of America settled AIB's case against it in 2012.
Lawyers for both AIB and Citibank have been working towards having their pre-trial submissions delivered to the New York court by October 30, after which a trial date could be set.
At the time they were uncovered, the rogue trading losses racked up by Mr Rusnak at Allfirst were some of the biggest on record. AIB sold Allfirst to US bank M&T in 2003.
Mr Rusnak pleaded guilty to bank fraud in 2002 and was sentenced to seven-and-a-half years in prison. He served six years. He currently runs a dry-cleaning business in Baltimore.