Whether U.S. President Donald Trump has the constitutional authority to extend federal unemployment benefits by executive order remains unclear. Equally up in the air is whether states, which are necessary partners in Trump's plan to bypass U.S. Congress, will sign on.

Trump announced an executive order Saturday that extends additional unemployment payments of up to 400 U.S. dollars a week to help cushion the economic fallout of the pandemic. 

Congress had approved payments of 600 U.S. dollars a week at the outset of the coronavirus outbreak, but those benefits expired August 1 and Congress has been unable to agree on an extension. 

Many Republicans have expressed concern that a 600-U.S.-dollar weekly benefit, on top of existing state benefits, gives people an incentive to stay unemployed.

But under Trump's plan, the 400 U.S. dollars a week requires a state to commit to providing 100 U.S. dollars.

Many states are already facing budget crunches caused by the pandemic. Asked at a news conference how many governors had signed on to participate, Trump answered: "If they don't, they don't. That's up to them."

Trump expressed a different view on Sunday night, following a day of state officials questioning how they could afford even 100 U.S. dollars per person in additional weekly payments. 

He said as he returned to Washington that states could make application to have the federal government provide all or part of the 400-U.S.-dollar payments. Decisions would be made state by state, he said.

Several state officials questioned how Trump's initial proposal would work and often expressed doubt that they could afford to participate at the level Trump initially set without using federal funds.

Aubrey Layne, secretary of finance for Virginia Gov. Ralph Northam, a Democrat, said in a phone interview Sunday he believes it would be feasible for Virginia to participate in such a program if states are allowed to use money that's been allocated to them under the already passed CARES Act. 

He added his preliminary understanding is that states can do so, but he and others are waiting to see the rules published.

The better solution, Layne said, would be for Congress to pass legislation.

Details about the program were confused on Sunday and that was even before Trump's declaration that states could ask the federal government to pay all or part of the 400-U.S.-dollar weekly payments.

Several advocacy groups that follow the issue, though, said it's clear the way the executive order is structured that the federal money will be contingent on states making a 25 percent contribution.

New York Gov. Andrew Cuomo, a Democrat, called the plan "an impossibility."

"I don't know if the president is genuine in thinking the executive order is a resolution or if this is just a tactic in the negotiation," Cuomo said. "But this is irreconcilable for the state. And I expect this is just a chapter in the book of Washington COVID mismanagement."