Washington — The Education Department issued new guidelines today for an emergency student-loan program that, after action last week by Congress, looks increasingly unlikely to be necessary.

In a 15-page letter, the department set out detailed terms for carrying out a “lender of last resort” loan program. The instructions were addressed to the nation’s 35 guarantee agencies, which are nonprofit entities that use federal money in the existing program of government-backed student loans to repay lenders when borrowers default.

Under lender-of-last-resort provisions, the guarantee agencies could be called upon to issue loans directly to students if too many loan companies decided they could not afford to issue government-backed loans at regular prices.

Education Department officials began making preparations for a lender-of-last-resort emergency several weeks ago, even though they said the withdrawal of some lenders from the government-subsidized system had not left any students unable to find loan money. Congress took another step to help students last week by passing legislation that would let the education secretary buy portfolios of loans from the loan companies, thereby giving them more cash to lend to more students.

Despite today’s 15-page letter setting out guidelines for operating a lender-of-last-resort system, the Education Department still hasn’t settled on how much it would pay the guarantee agencies as a fee for making emergency loans to students.

Department officials also have not decided what rates they will offer loan companies that seek to sell their loans to the secretary under terms of the legislation approved last week by Congress. “We hope to be able to provide answers in the near future” on that question, David Dunn, the department’s chief of staff, told reporters participating in a conference call this afternoon. —Paul Basken