UK ministers are "increasingly confident" more countries could be added to the amber and green list as international travel begins to return.
Foreign Secretary Dominic Raab said "the momentum forward is positive" a day after the government announced quarantine requirements for fully vaccinated US and EU travellers would be dropped.
The traffic light system for travel is to be reviewed next week.
"We've done the job we had to do domestically and as we see other countries catch up if you like, I think we are increasingly confident that more countries will go either on amber or on to green," Mr Raab told Sky News.
"We’re confident as we come out of lockdown in this country we’re in a lot stronger position."
However, ministers were told dropping quarantine requirements for vaccinated US and EU travellers posed a “clear public health risk” before the decision was announced, The Times reported.
From Monday, millions of fully vaccinated passengers from the US and EU will be able to enter England without the 10-day quarantine restriction.
Quarantine-free travel only applies to vaccines approved by regulators either in the UK, EU and US.
The move was welcomed by the travel industry, but scientists are concerned about the importation of new virus variants.
After an encouraging streak of declining Covid-19 case numbers, daily infections climbed to 27,734 with 91 deaths on Wednesday.
Mr Raab did not deny that ministers were told quarantine-free travel posed a health risk.
"We don't get homogenised advice ... you get the balance of opinion and then a clear steer based on it, which we then test," he told BBC's Radio 4 Today programme.
"We feel this is a modest opening up of international travel but one which has the reassurances that we can take further steps forward as we build confidence in the system."
UK travel: green, amber and red list countries
The main opposition Labour party said scheme was “reckless” and could allow a new variant to “run rampant” through the country.
“The government’s track record on our borders has been one of recklessness and confusion,” Shadow Transport Secretary Jim McMahon said.
“They are in danger of continuing this by setting out changes in policy, applying to England only, without the scientific data and criteria we need to make sure we don’t see another Johnson variant run rampant through the country and damage the effort of the British public.”
Scotland will follow England in dropping quarantine vaccinated EU and US passengers from Monday.
The Welsh government said it “regrets” the move but would also allow quarantine-free travel.
Northern Ireland is set to make a decision later on Thursday.
