Boris Johnson has urged other world leaders to hold firm in their long-term support for Ukraine, amid increasing concern in Downing Street that some countries could become swayed by calls for Kyiv to cede territory to Russia in exchange for peace. Arriving at the G7 summit in southern Germany, as his domestic political woes continued to swirl, Johnson used a string of bilateral meetings and TV interviews to present himself as a bulwark against potential backsliding by the US and other western states. The prime minister even connected the two situations, telling CNN that Vladimir Putin would not have been able to invade a sovereign neighbour if he too had “a committee of backbenchers” threatening to depose him for any mistakes. Outlining his key message for the G7 gathering, one he will reiterate later this week at a Nato summit in Madrid, Johnson said the financial cost of providing longstanding support to Ukraine was “a price worth paying for democracy and freedom”. “I would just say to people in the United States that this is something that America historically does and has to do,” he said. The global consequences of letting Russia prevail, Johnson added, would be “absolutely catastrophic”. Speaking to reporters at the annual G7 gathering, held amid ultra-tight security in the Bavarian countryside, Johnson warned of inevitable “fatigue in populations and politicians” as the conflict dragged on. “I think the pressure is there and the anxiety is there. We have got to be honest about that,” he said. While Downing Street stressed it does not as yet detect any G7 leaders trying to nudge Ukraine into accepting a humiliating peace, in which Russia would maintain control of eastern regions captured since February, this is a mounting concern. A Downing Street source said the sense of unity at the summit over Ukraine appeared strengthened by Sunday’s Russian missile attack on civilian targets in Kyiv. “It stiffened resolve,” they said. “There is a very strong sense of shared purpose.” Johnson is to urge other leaders to step up efforts to get grain supplies out of Ukraine amid a blockade by Russia, seen as a way for Moscow to pressure western countries into backing down over fears of famine in developing nations. While the UK is wary about direct action to help ships depart – Johnson’s spokesman noted the “need to be mindful of anything that could be perceived as escalatory” – the prime minister has pledged to find other means to get grain out, saying “nothing should be off the table”. He is also seeking new sanctions on Russia, having already announced a joint ban on imports of Russian gold, along with the US, Canada and Japan. Johnson also said he would very happily host Volodymyr Zelenskiy should he find it possible to visit London, while conceding this seemed unlikely. The Ukrainian president is due to appear virtually at both the G7 and Nato summits. One leader with whom Johnson was not expected to have a meeting at the summit was the US president, Joe Biden, with No 10 insisting this was purely down to mutual scheduling issues and not a snub. His schedule on Sunday saw him hold one-to-one talks with the French president, Emmanuel Macron, the German chancellor, Olaf Scholz and the Canadian prime minister, Justin Trudeau, with Ukraine playing a central part in all of the talks. Johnson and Trudeau even began their talks with a mocking reference to Putin’s penchant for ultra-macho, topless official photographs. A suggestion they remove their jackets amid the heat prompted Trudeau to jokingly suggest “a bare-chested horseback ride”, while Johnson said they could “show our pecs”. While the UK and France have not always agreed on the issue of Ukraine, Downing Street insisted Johnson and Macron were in full agreement on Sunday. Johnson’s official spokesperson said that while the UK was confident about a robust post-summit G7 message on Ukraine, it was nonetheless the case that world leaders could become increasingly swayed by thoughts of pushing Zelenskiy into accepting a Russian peace deal. “You can understand why people feeling the challenges of this global cost of living crisis might question why countries are spending so much time on this issue,” he said. In what could be seen as a pointed omission, asked just before a bilateral meeting with Macron about whether France and Germany were doing enough over Ukraine, Johnson only mentioned the German response. “I never believed in my lifetime that I would see a German chancellor stepping up in the way that Olaf Scholz has and sending weaponry to help the Ukrainians to protect themselves,” he said. “He has made huge, huge strides. We have 4% of our gas comes from Russia; in Germany, it’s 40%. They are facing real, real pressures, they are having to source energy from elsewhere. But they are doing it. They are making the effort. They are making the sacrifice. That’s because they see that the price of freedom is worth paying. “This is something that it’s worth us standing up for together. And that is the principle that a free, independent sovereign country like Ukraine should not be violently invaded and should not have its boundaries changed by force.” Johnson sought to dodge any new controversies, with the official UK readout of the meeting with Macron failing to even mention their discussion about the French president’s plans for a semi-detached “European political community” of non-member nations, potentially including the UK. French officials, in contrast, said Johnson had shown “a lot of enthusiasm” for the idea, although No 10 stressed this could only be the case if the still-nascent plan did not include elements of freedom of movement, as mooted. Similarly, while Johnson used the CNN interview to stress the need for democracy, he declined to comment on the ongoing US hearings into the January attack on the Capitol by supporters of the former president Donald Trump, saying: “In principle we shouldn’t talk about each other’s domestic politics.” Johnson arrived at the talks from Rwanda, where he had been taking part in a Commonwealth summit, part of an overseas trip totalling nine days that is keeping him away from an increasingly turbulent political situation at home.