The United States, Britain and the European Union should act jointly to put more pressure on Belarusian President Alexander Lukashenko and his government, opposition leader Sviatlana Tsikhanouskaya told Reuters on Friday. Tsikhanouskaya made the comments during a visit to Warsaw, Poland ahead of a summit of the G7 rich countries in Britain next week, at which she hopes issues raised by the Belarusian opposition will be addressed. Belarus has shot up the international agenda since it forced down a Ryanair flight over its air space and arrested an opposition journalist last month. "Pressure is more powerful when these countries are acting jointly and we are calling on [the] UK, the USA, the European Union and Ukraine. They have to act jointly so their voice will be more loud," Tsikhanouskaya said. France has said it would like to invite the Belarusian opposition to the G7 summit, if host country Britain agrees. Britain has said there are no plans to invite further delegations, but that Belarus would be discussed. read more Tsikhanouskaya said she had not been invited to the summit but expected Belarus would be discussed there. Britain, the United States and the European Union all imposed bans and asset freezes on some Belarus officials after an election last year that the opposition says was rigged. Since the Ryanair incident, Western countries have discouraged their airlines from flying over Belarus and said they will take other steps, such as barring Belarusian airlines and adding more names to their blacklists. Some opposition figures have called for stronger measures that would have an impact on the overall Belarusian economy, such as restrictions on imports of minerals or oil from Belarus.