TOKYO, Aug 4 (Reuters) - Japan's health minister on Wednesday signalled the government may consider rolling back a controversial new policy asking COVID-19 patients with less serious symptoms isolate at home rather than going to the hospital.

The comment, which came amid rising criticism over the policy, underscores Tokyo's struggle in dealing with a spike in Delta variants that is overshadowing the Olympic Games.

Prime Minister Yoshihide Suga announced on Monday only COVID-19 patients who are seriously ill and those at risk of becoming so will be hospitalised, while others isolate at home, a shift in policy some fear may lead to an increase in deaths.

Health Minister Norihisa Tamura defended the policy shift, saying that by asking people with less serious symptoms to isolate at home, Japan can ensure it does not run out of hospital beds for people in need of intensive care.

"The pandemic has entered a new phase ... Unless we have enough beds, we can't bring people into hospitals. We're acting pre-emptively on this front," Tamura told parliament.

"If things don't turn out as we expect, we can roll back the policy," he said, adding that the policy shift was a move to deal with the unexpectedly fast spread of the new variant.

The outcry is another setback for Suga, who has seen support plunge due to his handling of the pandemic ahead of general elections to be held this year.

Opposition parties agreed on Wednesday to ask the government to abandon the hospitalisation policy, according to Kyodo news agency.

Even a lawmaker from New Komeito, a coalition partner of Suga's ruling Liberal Democratic Party, urged for a review or roll back.

Japan has seen a sharp increase in coronavirus cases. Tokyo, which had a record high of 4,058 new infections on Saturday, had 3,709 new cases on Tuesday.

Suga and Olympics organisers say there is no link between the July 23-Aug. 8 Summer Games and the sharp increase in cases.

But Shigeru Omi, Japan's top medical adviser, told parliament the hosting of the Games may have affected public sentiment, suggesting the event was eroding the effect of government requests for people to stay home.

Imposing a nationwide state of emergency could be an option to deal with the pandemic, he said. States of emergency are already in place in several prefectures, as well as Tokyo.

"Political leaders are sending out messages to the public in earnest, but probably not as strongly and consistently as hoped," Omi said. "We're seeing COVID-19 clusters emerge more broadly including at schools and offices," he said.