BY JOSH MITCHELL AND COREY BOLES
WASHINGTON—A bitter lobbying battle between corporate titans Boeing Co. and Delta Air Lines Inc. has ensnared a small agency playing a big role in the Obama administration’s drive to boost exports.
The White House has tried unsuccessfully for months to get Congress to renew and expand the lending authority of the Export-Import Bank, which provides loan guarantees and other assistance to overseas customers of U.S. companies at below-market rates.
The bank—overseen by a White House appointee and funded by customer fees and interest payments—has doubled its financial support in the past four years to $41 billion annually. But without congressional …