James Saft is a Reuters columnist. The opinions expressed are his own.

HUNTSVILLE, Ala. — We finally have an answer for what kind of financial service only a too-big-to-fail bank can provide: a record-setting loan to fund a takeover that will hugely reduce competition in U.S. wireless communications.

AT&T on Monday said it would pay $39 billion for Deutsche Telekom AG’s T-Mobile U.S. wireless unit, backed by $20 billion of financing from JPMorgan Chase & Co.

The deal, which is subject to regulatory approval, will leave AT&T and Verizon Wireless in control of 80 percent of the U.S. market for contract customers, according to rival Sprint Nextel Corp.

The one-year unsecured bridge loan has an 18-month commitment period, meaning it can be drawn any time during that time when AT&T is ready, and is the largest ever such loan made by JP Morgan Chase, a bank with more than 200 years of institutional history.

While there have been M&A loans this big before, the vast majority would have been syndicated among a consortium of banks to reduce risk.