US lawmakers have rejected a short-term funding bill for homeland security, increasing the threat of a partial agency shutdown.
The House of Representatives voted 224-203 against the measure, with dozens of Republicans defying party leaders.
They rejected the bill after provisions to block parts of President Barack Obama's immigration plan were dropped.
A partial closure could still be avoided if the House passes a Senate-backed deal before 05:00 GMT.
That deal would ensure full funding for the Department of Homeland Security for one week, giving both sides more time to agree on a long-term deal. It was passed on a voice vote in the Senate on Friday evening, but still needs approval from the House.
The Department of Homeland Security, which employs about 250,000 people, is responsible for securing US borders, airports and coastal waters.
About 200,000 "essential" department employees will continue to work without pay if the agency does not have funding.
Effects of a Homeland Security shutdown
- Airport security agents required to work without pay
- Employers would not have the ability to use a programme called E-Verify to check if new employees are authorised to work legally in the US
- No grants made to local and state authorities, including for training and new equipment
- Secret Service will not be able to hire agents to protect 2016 presidential candidates
- Civil rights and civil liberties complaint lines and investigations will be shut down