Talks between US Republicans and Democrats to reach a border security agreement and avoid another government shutdown have stalled, reports say.
Negotiators had wanted a deal by Monday to give Congress time to pass legislation by Friday, when last month's federal funding deal runs out.
The previous shutdown, lasting 35 days, was the longest in US history.
The disagreement centres on President Donald Trump's insistence on a bill that funds a US-Mexico border wall.
The latest impasse has arisen because Democrats want officials from Immigration and Customs Enforcement (ICE) to concentrate on detaining migrants with criminal records instead of those who have overstayed their visas by limiting the number of beds its detention centres have, the New York Times reported.
Democratic negotiators were hoping to cap the number of beds at 16,500. That is roughly the number of people detained in the last years of the Obama White House, the Washington Post says.
Negotiators had also been looking at between $1.3bn and $2bn in funding for Mr Trump's proposed border wall, a long way off the $5.7bn the president has been demanding, reports said.
On Sunday, lead Republican negotiator Senator Richard Shelby told Fox News that he was "not confident we're going to get there".
"I'll say 50-50 we get a deal," he said, adding: "The spectre of a shutdown is always out there."
Mr Trump suggested that Democratic leaders were preventing negotiators from reaching an agreement.
Last month he said the talks were a "waste of time".
A new shutdown could see federal agencies including the Homeland Security, State, Agriculture and Commerce Departments lose access to money and begin to shut down again.
It would affect about 800,000 federal employees, who would go unpaid. During the last shutdown, some employees continued to work unpaid but many others called in sick.
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