WASHINGTON—The Obama administration is telling federal agencies to prepare for a possible government shutdown.

The Office of Management and Budget sent a letter to agency heads this week ordering them to make contingency plans if Congress does not reach a deal to fund the government after Sept. 30. The letter from OMB director Sylvia Burwell says there is still enough time for Congress to prevent a lapse in funding, but "prudent management" requires that the government get ready for a shutdown.

House Republicans plan to vote on a budget bill this week that withholds funding for President Barack Obama's health care law. But the effort stands little chance in the Democratic-controlled Senate.

OMB has sent similar warnings to agencies during previous budget battles.