WASHINGTON - As the White House refused to rule out the possibility that the federal government would shut down again, negotiators clashed over whether to limit the number of migrants authorities can detain, creating a new hurdle for a border security compromise acceptable to Congress.

With a Friday deadline approaching, the two sides remained separated over how much to spend on US President Donald Trump's promised border wall. But rising to the fore on Sunday was a related dispute over curbing Immigration and Customs Enforcement, or ICE, the federal agency that Republicans see as an emblem of tough immigration policies and Democrats accuse of often going too far.

The fight over ICE detentions goes to the core of each party's view on immigration. Republicans favor rigid enforcement of immigration laws and have little interest in easing them if Democrats refuse to fund the wall bordering Mexico. Democrats despise the proposed wall and, in return for border security funds, want to curb what they see as unnecessarily harsh enforcement by ICE.

People involved in the talks said Democrats have proposed limiting the number of immigrants the agency can detain after caught residing illegally inside the United States - not at the border. Republicans said they don't want that cap to apply to immigrants caught committing crimes, but Democrats do.

Democrats said they proposed their cap to force ICE to concentrate its internal enforcement efforts on dangerous immigrants, not those who lack legal authority to be in the country but are productive and otherwise pose no threat. Democrats have proposed reducing the current number of beds ICE uses to detain immigrants who are in the country illegally from 40,520 to 35,520.

But within that limit, they've also proposed limiting to 16,500 the number for immigrants to be apprehended for residing illegally within the US, including criminals. Republicans want no caps on the number of immigrants who've committed crimes that can be held by ICE.

Trump used the dispute to cast Democrats as soft on criminals.

"I don't think the Dems on the Border Committee are being allowed by their leaders to make a deal. They are offering very little money for the desperately needed Border Wall & now, out of the blue, want a cap on convicted violent felons to be held in detention!" Trump tweeted on Sunday.

Acting White House chief of staff Mick Mulvaney, in appearances on NBC's Meet the Press and Fox News Sunday programs, said "you absolutely cannot" eliminate the possibility of another shutdown if a deal is not reached over the wall and other border matters.

Associated Press