WASHINGTON (Reuters) - Current and former CEOs of three major US financial institutions deeply involved in the widening sub-prime mortgage crisis were asked this week by a Congressional committee to testify at a hearing next month on their massive pay and severance packages.

A House panel invited Countrywide Financial CorpCEO Angelo Mozilo, former Citigroup Inc CEO Charles Prince and former Merrill Lynch & Co Inc CEO Stanley O'Neal to appear and answer questions on February 7.

House Oversight and Government Reform Committee chairman Henry Waxman, a 17-term California Democrat, said he was seeking testimony from the executives as part of an "ongoing investigation into executive pay".

In a letter on the hearing sent to Mozilo, Waxman wrote: "According to recent press reports, if Bank of America Corp completes its proposed purchase of Countrywide Financial, you stand to collect tens of millions of dollars in severance payments and other compensation."

Waxman asked Mozilo to be prepared to explain how his compensation package aligns with shareholders' interests and whether it "is justified in light of your company's recent performance and its role in the national mortgage crisis".