Prime Minister Yoshihide Suga on Tuesday reiterated his pledge to secure enough COVID-19 vaccines for Japan's entire population by the first half of next year after a U.S. drugmaker said its experimental vaccine proved more than 90 percent effective.

"We will continue to negotiate with firms both in Japan and abroad" to ensure Japan can purchase enough doses, Suga said during a House of Representatives session.

Pfizer Inc. has said the efficacy of its vaccine, developed with German partner BioNTech SE, was proved in a late-stage clinical study with more than 43,000 participants.

Japan has agreements to receive 120 million doses of any successfully developed vaccine each from Pfizer and Britain's AstraZeneca Plc, and a further 50 million doses from U.S. biotechnology firm Moderna Inc. -- enough for the country's population to take the necessary two doses.

Suga said Japan would conduct the approval process for any vaccine "based on the latest scientific knowledge and with a priority on safety and effectiveness."

Japan's parliament on Tuesday began deliberations on legislation to facilitate the distribution of a vaccine, with provisions for the government to shoulder all of the costs and take responsibility for unforeseen side effects.

Related coverage:

Japan PM Suga orders compilation of 3rd extra budget for pandemic stimulus

Pfizer's experimental vaccine over 90% effective in fighting COVID-19

Japan to prioritize elderly in administering coronavirus vaccines

While the legislation obliges the population to "make an effort" to be vaccinated, it will not be strictly mandatory and there should be no discrimination against those who choose not to do so, Suga said.

Japan has not seen an explosive spread of the novel coronavirus like the United States and some other parts of the world, but the number of new daily confirmed cases has continued to rise in recent weeks, prompting a government subcommittee of health experts to call for stepping up preventative measures.

Speaking at a coronavirus task force meeting, Suga said the government is "dealing with the situation with maximum vigilance."

There were 1,284 newly confirmed cases in the country on Tuesday, bringing the cumulative total to 111,222, according to a Kyodo News tally based on official data, including around 700 from a cruise ship that was quarantined in Yokohama in February. The death toll stood at 1,864.

While the biggest sources of infections were still Tokyo and Osaka, there continued to be a worrying increase of clusters in northern regions such as Hokkaido, a popular tourist destination for its nature and cuisine.

Hokkaido Gov. Naomichi Suzuki met with Suga on Tuesday to ask for help in curbing the outbreak, including by setting guidelines on preventative measures heading into the winter and dispatching additional medical personnel.