Gov. Charlie Baker is looking to assert his authority and keep construction projects open — but Boston Mayor Martin Walsh is doubling down and extending the city’s construction shutdown indefinitely amid the coronavirus outbreak.

“The safety and health of construction workers and all residents of Boston is my first priority, and I am not willing to put that at risk as the virus spreads throughout our communities,” Walsh said in a statement in which he extending the two-week shutdown “until further notice.”

But this comes as Baker looks for cities to get rid of their bans. Earlier on Wednesday, Baker’s chief legal counsel Robert Ross sent a letter on Wednesday to all of the chief executives of Massachusetts’ cities and towns, aimed at giving “guidance” over the order the governor issued on Monday that shut down all work deemed “non-essential.”

The letter singles out the construction industry, as portions of the order “designate construction projects as COVID-19 essential services” — even though Boston, Cambridge, Somerville and more have put bans into place.

“Local policies, regulations or directives that provide otherwise are in direct conflict with this Order and should be withdrawn,” the letter states.

“The Baker-Polito Administration recognizes the value of local decision making in most circumstances. Nevertheless, ensuring an effective response to the COVID-19 emergency requires the Administration to prioritize consistency and clarity of action,” the letter says, citing the state of emergency as grounds for superseding local control.

Baker’s office didn’t immediately respond to a request for comment.

Somerville and Cambridge also aren’t getting ride of their bans. Somerville Mayor Joe Curtatone also said in a statement that his city’s moratorium “remains in full force.”

The city had at first just issued some restrictions, but then moved to shut down all construction this week.

“Upon review of those plans and through spot site checks, we discovered we could not at this time control for every factor to ensure safe social distancing and other health and safety guidelines, particularly due to Somerville’s dense urban environment,” Curtatone said in a statement.

Cambridge spokesman Lee Gianetti said, “The City of Cambridge’s Temporary Emergency Construction Moratorium of March 18, 2020 will remain in effect while the City Solicitor in consultation with the City’s Commissioner of Public Health reviews the Governor’s announcement of this afternoon.”

Medford, which had put some restrictions in place, announced it was lifting them following Baker’s letter.