The Foreign Secretary told BBC One's The Andrew Marr Show there was a "risk" of a third spike in case numbers "if we don't get the balance right".
He said: "But so far the R level is coming down - that's really important - and that's why we're starting with the tiered approach."
But asked whether there would be another national lockdown if people fail to comply with the rules, Mr Raab said: "We're doing everything we can to avoid that."