A battle in Congress that could shut down the U.S. Export-Import Bank next week is already causing headaches for small exporters as they try to stop customers from defecting to foreign competitors and as export financing starts to freeze up.

Smaller firms may be the biggest initial victims if the bank has to stop operating.

China's medium- and long-term official export credit support jumped to $58 billion last year from $28.3 billion in 2011, according to a recent U.S. Ex-Im report.

Trina has previously had support from the China Ex-Im bank, disclosing in Securities and Exchange Commission filings that it repaid a $40 million working capital loan from the bank last year.

Trade bankers say the U.S. Ex-Im's demise would leave a gap in trade financing that would be hard for the private sector to fill, and a freeze on new Ex-Im deals is already starting to take hold.

One small firm, industrial blower-maker Sonic Air Systems Inc., has given up Ex-Im trade insurance by assuming foreign payment risk on its own.

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