LONDON — British Prime Minister Boris Johnson on Friday defended his government's coronavirus restrictions as "the right and responsible thing to do" in the fight to curb the spread of coronavirus in the country.

"Taking action is the right and responsible thing to do," the prime minister said at a virtual press conference at Downing Street.

"Without action our health service will be overwhelmed," he said. "I want to avoid another national lockdown."

The British government's three-level COVID-19 alert system came into force in England on Wednesday.

Under the Tier Two of the alert system, millions of Londoners will face tougher measures from Saturday with different households banned from meeting in indoors, including in pubs and restaurants.

Lancashire will join Liverpool and move into Tier Three, the top level of England's COVID restrictions from Saturday. The "very high" alert level means pub closures and bans on household mixing indoors, in private gardens and most outdoor venues.

Meanwhile, Johnson said Britain has "started building the domestic infrastructure" to offer more rapid tests which could provide results in as fast as 15 minutes.

The government plans to "start distributing and trialling tests across the country...In time we want to use tests to keep open more parts of the economy that have sadly been closed." Johnson said.

Talking about Greater Manchester Mayor Andy Burnham's reluctance to move the city to Tier Three restrictions, Johnson said he "completely" understands.

But faced with the "grave" situation, Johnson said he might "have to intervene", adding that efforts will be "more effective" if the British government and the local government work together.

To bring life back to normal, countries, such as Britain, China, Russia and the United States are racing against time to develop coronavirus vaccines.