Liverpool's schools will not reopen "until mid-June at the very least", the city's council has said.
The government wants primary schools to restart in a phased way from 1 June.
But Steve Reddy, director of children and young people's services in Liverpool, said "we simply cannot reopen" by then.
"Our guiding principle is that schools can only re-open to other pupils when it is safe to do so and not a moment before," he said.
In a letter to parents, he wrote: "The layout of every school is different and they all have different challenges... in terms of maintaining social distancing and hygiene.
"There is no doubt in my mind that we simply cannot reopen schools in line with the suggested timetable outlined by the government."
Only school services for vulnerable children and the children of key workers will continue in Liverpool from 1 June, after the half-term break.
Education Secretary Gavin Williamson said the government was giving educational providers "all the guidance and support they will need" for a phased return in June.
"Getting children back to school is vital for their educational development and many schools are already taking steps to welcome back their pupils," he said.
However, an alliance of nine teachers' unions has warned it is not yet safe to reopen, while The British Medical Association agreed it was too early.
Earlier this week, Liverpool mayor Joe Anderson said that, in the city, "the curve of this disease is still far higher than other parts of the country and I want to make sure children returning to school are in the safest environment".
Mr Reddy said each school's restart date would vary, based on its head teacher's assessment.
"All I can say at this stage is that we do not envisage primary age pupils being able to return until mid-June at the very least," he said.
"The government has made it clear they will not be fining parents for not sending children into school during this term."
He said the council would "not be pressuring anyone to send their child to school" but advised those who receive support from social workers to follow their advice.