San Francisco will begin moving up to 400 homeless people into the cavernous Moscone West convention center on Thursday, part of a larger sheltering effort that includes everything from hotel rooms to federal trailers during the coronavirus outbreak.

The details on the attempt to prevent a widespread outbreak of the coronavirus among homeless people — and those they might encounter on the streets — were laid out Wednesday in an online briefing by city officials.

However, Mayor London Breed said any program will stop short of opening up private hotel rooms to the city’s homeless population in general, as some advocates and supervisors have proposed.

“I wish it were that easy to help people who are struggling with addiction, who are struggling with mental illness,” Breed said. “The wraparound supportive services (needed) for these populations make it difficult to just open the doors and allow anyone to walk in.”

The abrupt repurposing of Moscone West is aimed at homeless people already spending the night in shelters — where cots traditionally have been spaced just 3 feet apart rather than the 6 feet recommended for safe social distancing during the pandemic.

The first 30 short-term residents are expected to move into Moscone West on Thursday, with another 30 on Friday and increasing numbers after that. In addition to a roof, a cot and full meals, they can expect “showers, television, amenities and other entertainment,” said Trent Rhorer, the head of the city’s Human Services Agency.

The city is also in negotiations to lease two other buildings that could be used to make sure no city-run shelters are too tightly packed.

As for moving people into private hotels, the city’s first priority for now is homeless people who have tested positive for COVID-19 but do not require hospitalization and can live on their own with minimal supervision. Homeless people with underlying health conditions or are age 60 and up would be next. The third group are health care providers — doctors and nurses, for instance — who can rest between shifts.

The city has made arrangements with six hotels offering 479 rooms. According to Rohrer, 123 homeless people have moved in and 10 have declined the offer of assistance. Another 2,000 rooms in three hotels could be available by early next week.

As for the 91 federal trailers, they haven’t yet been deployed. They will be reserved, Rohrer said, for currently homeless people “who need to isolate, but have significant other needs,” such as addictions or behavior problems that require supervision.

Breed began the briefing by praising San Franciscans who continue “showing up to work and providing help and support and assistance to others.” She also emphasized the imposition of tighter restrictions on being out in public, such as the closing of playgrounds and dog parks.

The mayor also made clear that, given the uncertainty surrounding efforts to contain the pandemic, the newest shelter-in-place timeline — through May 3 — is subject to change.

“The likelihood the May 3 date will be extended is possible,” Breed said.

John King is a San Francisco Chronicle staff writer. Email: jking@sfchronicle.com Twitter: @johnkingsfchron