Hours after two groups of governors announced that they were forming regional working groups to help plan when it would be safe to ease restrictions and reopen their economies, President Trump asserted in a White House news briefing that the authority to make such decisions rested with him.

“The president of the United States calls the shots,” Trump said. “They can’t do anything without the approval of the president of the United States.”

The announcements by the governors, who formed groups on both coasts, came hours after the President wrote on Twitter that such a decision lies with the President, not the states, and before he made the point more forcefully to reporters in Washington.

Asked what provisions of the Constitution gave him the power to override the states if they wanted to remain closed, he said, “Numerous provisions,” without naming any.

His day-long assertions of power appeared to have little effect on the governors.

“Well, seeing as we had the responsibility for closing the state down,” governor Tom Wolf of Pennsylvania said, “I think we probably have the primary responsibility for opening it up.”

Wolf and the governors of Connecticut, Delaware, Massachusetts, New Jersey, New York and Rhode Island agreed to create a committee of public health officials, economic development officials and their chiefs of staff.

On the West Coast, the governors of California, Oregon and Washington also announced Monday a joint approach to reopening economies that they called a Western States Pact. “Our states will only be effective by working together,” they said in a joint statement.

Governor Gavin Newsom of California said he had been in discussions with the other governors to coordinate efforts on the West Coast. He said that on Tuesday he would outline the “California-based thinking” on reopening and promised it would be guided by “facts”, “evidence” and “science”.

Governor Andrew M. Cuomo of New York said that some East Coast states would form a working group to develop a plan for reopening the region.

The stay-at-home orders that have kept a vast majority of Americans indoors were issued state by state, by their governors.

The President did issue non-binding guidelines urging a pause in daily life through the end of the month.

The potential power struggle threatens widespread confusion if the President and governors end up at loggerheads over how and when to begin resuming some semblance of normal life in the country once the risk of the virus begins to fade sufficiently.

Conflicting orders by Washington and state capitals would leave businesses and workers in the untenable position of trying to decide which level of government to listen to when it comes to reopening doors and returning to their jobs.