Duke Energy Corp. (DUK) and Progress Energy Inc. (PGN) announced Monday that they secured a combined $6 billion in credit from 30 lenders, with three Chinese banks providing 11% of the total.

Duke plans to buy Progress in an all-stock deal valued at about $13.7 billion that the companies have said they hope to close by the end of this year. The merger, which requires the approval of federal and state regulators, would create the nation's largest utility.

Duke, which has access to $4 billion of the total credit line, pointed out that the Chinese government-owned Bank of China Ltd. (3988.HK, 601988.SH, BACHY) and Industrial & Commercial Bank of China Ltd. (1398.HK, 601398.SH, IDCBY) agreed to provide $305.5 million each, more than 10% of the total. China Merchants Bank Co. Ltd. (3968.HK, 600036.SH, CIHHF) is providing $46 million.

China Merchants Bank is independent, though indirectly controlled by the Chinese government through a number of wholly owned companies that hold shares in the bank, according to documents issued by the U.S. Federal Reserve Bank.

"It was a nice coming together of China's desire to bank with businesses outside China and our desire to diversify the banks" with which Duke does business, said Duke spokesman Tom Williams.

The Chinese banks' participation in the U.S. utilities' financing deal comes as Chinese banks, which include some of the world's largest, look to expand overseas. The investment is welcomed by U.S. companies like Duke, that want to spread their banking relationships across more institutions, particularly in regions other than the U.S. and Europe.

Williams said the agreement with the Chinese banks was a direct result of Duke's partnership with Chinese companies including ENN Energy Holdings Ltd. (2688.HK, XNGSF) and China Huaneng Group.

In December, Duke said it signed an agreement with ENN to exchange knowledge on advanced energy and building technologies and work with ENN on an "eco city" ENN was building in Langfang, China. The two companies signed an agreement in 2009 to develop U.S. solar power projects.

In August 2009, Duke signed a similar agreement with China Huaneng Group, a government-owned enterprise that owns several energy subsidiaries including power-plant operator Huaneng Power International Inc. (0902.HK, 600011.SH, HNP).

Duke and ENN haven't built any U.S. solar power projects to date, owing in part to an inability by ENN to benefit from tax credits that the U.S. government offers for such projects.

Under the credit agreement announced Monday, Duke has access to $4 billion in credit and Progress has access to $2 billion, with the amounts to be combined following the companies' merger. The agreement replaces a $3.14 billion line of credit Duke had that was set to expire in June 2012. It also replaces three credit facilities totaling $2 billion that Progress had, that expired in 2012 and 2013.

Duke plans to use the credit line primarily to support its issuance of commercial paper, although it could also be used for short-term debt, the company said.

Wells Fargo & Co. (WFC) served as administrative agent, and Bank of America Corp. (BAC) and Royal Bank of Scotland Group PLC (RBS.LN, RBS) served as syndication agents for the credit agreement. Documentation agents included units of Bank of China; Industrial and Commercial Bank of China; Barclays PLC (BARC.LN, BCS); Citigroup Inc. (C); Credit Suisse Group AG (CS, CSGN.VX); JPMorgan Chase & Co. (JPM); and UBS AG (UBSN.VX, UBS).

-By Cassandra Sweet, Dow Jones Newswires; 415-439-6468; cassandra.sweet@dowjones.com