WASHINGTON — When Representative Dana Rohrabacher, Republican of California, visited Honduras early this year to congratulate the newly elected president, the congressman showed up with an unusual delegation.

There at his side was not just the typical collection of Washington foreign policy aides, but also a group of California real estate investors and businessmen, including a dealer in rare coins, and top executives from a fledgling San Diego biofuels company run by a friend of the congressman’s wife.

Using his status as a senior Republican on the House Foreign Affairs Committee, Mr. Rohrabacher cheered his hosts in Honduras by openly challenging the Obama administration’s foreign policy agenda there, then arranged a series of meetings with top Honduran officials, including the president, during which the congressman “enthusiastically promoted” the biofuel company’s plans to perhaps set up operations in Honduras, says a State Department summary of the meetings included in the files obtained by WikiLeaks.

The country was eager to accommodate the congressman — who said in an interview that his actions were entirely appropriate and reflected his activist approach to foreign policy — given that the previous Honduran president had been forced out of office and into exile, and the new government was angling for United States support.