Express Scripts is syndicating a $14 billion bridge loan that will help finance its $29.1 billion acquisition of rival Medco Health Solutions, banking sources said weekend.

The 364-day bridge loan, being arranged by Credit Suisse and Citigroup, is the biggest loan underwriting since a $20 billion underwriting done solely by JP Morgan in March to help AT&T raise money to buy T-Mobile USA from Deutsche Telekom.

Express Scripts on Thursday announced an agreement to buy Medco for $71.36 per share to create a powerhouse in managing prescription drug benefits.

The jumbo M&A loan is a benchmark deal for the U.S. and global loan market and sends a clear message of confidence that banks are able to underwrite multibillion-dollar loans despite difficult capital market conditions.

“Size is always challenging, but this company hits all of the points in terms of ability to syndicate, ability to access the bond market, the stability of the business, and it’s a name that people have a lot of familiarity with,” said a banker close to the deal.

The $14 billion, 364-day bridge loan will be replaced by permanent bond and loan financing shortly. A $5.5 billion permanent loan facility will be syndicated in August, the bankers said.

It will consist of a $4 billion funded five-year term loan A and a $1.5 billion five-year revolving credit, they added. Pricing on the term loan A is expected to open at 175 basis points over LIBOR.

“We have committed financing in place, but are not providing additional details at this time,” a spokesperson for Express Scripts said.