LONDON, July 1 (Reuters) - Prime Minister Boris Johnson said on Thursday he was confident Britons fully vaccinated against COVID-19 would be able to travel abroad this year. Britain permitted limited quarantine-free travel in May and June, and is trying to encourage other European countries to accept British travellers. The British government has said it will this month set out details of plans to allow those who have had both COVID-19 vaccine shots to avoid self-isolation on return from top tourist destinations such as Spain and France. "I"m very confident that the double jabs will be a liberator, and they will enable people to travel," Johnson told reporters. A rule change could be in effect by July 26, the first full week of the British school holidays, The Times newspaper reported. Johnson said the government would provide more details of its plans "in the course of July, in the course of the next few days." Business minister Kwasi Kwarteng said the government was in talks with European Union countries to ensure British travellers who have had two vaccine doses do not face restrictions. Italy, Portugal and Spain have tightened their entry requirements following a rise in COVID-19 cases in Britain caused by the more infectious Delta variant. Johnson is due on Friday to discuss travel restrictions with German Chancellor Angela Merkel, who has been lobbying the EU to take a more unified approach on travel rules to stop the spread of the Delta variant. read more The Times said Britain was close to agreeing a deal with Brussels for its National Health Service (NHS) app to be accepted by the EU as proof of a double vaccination. In return, Britain would accept a new EU digital certificate allowing travel, it said.