WASHINGTON, July 13 (Reuters) - Banks should be cautious of lending to people not legally authorized to work in the United States, as their income may be less reliable or they may be deported, a pair of U.S. bank regulators cautioned the industry Monday.

In new guidance, the Office of the Comptroller of the Currency, which supervises the nation's largest banks, and the Federal Deposit Insurance Corporation said non-citizens working in the U.S. illegally may have "less reliable" income and as a result may be a higher credit risk. The National Credit Union Association, which monitors credit unions, also issued the guidance.

"When a borrower's income is derived from employment that is not legally authorized, the source of repayment may be less reliable and may present increased credit risk," the guidance stated. Among reasons repayment could be riskier include loss of employment due to nonlegal status, an inability to become legally employed, or a borrower's removal from the United States.

The guidance, which is nonbinding and does not impose new requirements on banks but rather reminds them of existing obligations, is an effort to implement an executive order signed by President Donald Trump in May.

That order focused on the potential misuse of financial services by people living in the U.S. illegally and directed the Treasury  Department and other agencies to identify potential red flags for the industry. That order was a lighter touch than one feared by the banking industry and considered by the Trump administration, which would have directed banks to collect citizenship data on accountholders.