"But until now we haven't offered a positive alternative that reflects our values, our standards and our way of doing business".
The collective steps include slashing the time taken to develop and license vaccines, treatments and diagnostics for any future disease to under 100 days, while reinforcing global surveillance networks.
"The #CarbisBayDeclaration marks a proud and historic moment for us all", Mr Johnson said on Twitter, as world leaders kicked off the second day of their three-day summit.
"It's welcome that G7 leaders are planning measures to end future pandemics faster, but the lack of urgent action to end the current crisis is unforgiveable", its health policy manager Anna Marriott said.
After an opening session on "building back better" from Covid-19, the leaders spent the evening at a reception hosted by Queen Elizabeth II at Cornwall's Eden Project, a renowned attraction showcasing the world's ecological riches.
"Under this agreement, the world's leading democracies will commit to preventing a global pandemic from ever happening again, ensuring the devastation caused by COVID-19 is never repeated".
The G7 will on Sunday discuss tackling climate change and safeguarding global biodiversity, laying the groundwork for the UN's pivotal COP26 environmental summit in Scotland in November.
And he said the United Nations agency would examine a British proposal to create a "Global Pandemic Radar" to send early warnings of future outbreaks.
The agenda broadened Saturday to foreign policy issues, as the G7 was joined by the leaders of Australia, South Africa and South Korea, with India taking part remotely.
However, Oxfam said the declaration "does nothing to address the fundamental problems that are preventing vaccines being accessible to the vast majority of humanity".
"This is not about making countries choose between us and China", said one senior Biden administration official, outlining the plan for reporters on condition of anonymity.
"We're pushing for being specific on areas like Xinjiang where forced labor is taking place", the official said, referring to the territory in northwest China where tens of thousands of Uyghurs have been forcibly transferred from their homes and assigned to factories across nine provinces in a range of supply chains including electronics, textiles and automobiles.
Joe Biden, Emmanuel Macron and Ursula von der Leyen during the G7 Summit in Cornwall today.
"This is about providing an affirmative, positive, alternative vision for the world than that is presented by China and, in some similar ways but also in some different ways, Russia", the official said.
Biden planned to press the other leaders to make clear that they believe forced labour practices are an affront to human dignity and "an egregious example of China's unfair economic competition".
The US president will also seek to address frayed relations with Moscow, in particular over its cyber activity.
During their meeting, World leaders at the G7 summit plan to meet about the importance of a "fair, sustainable, inclusive global economy", including a discussion about China.
In a rare interview with United States media released Friday, Putin voiced hope that Biden would be less impetuous than Donald Trump, who infamously sided with the Russian leader against the views of his own intelligence chiefs.
"It is my great hope that, yes, there are some advantages, some disadvantages, but there will not be any impulse-based movements on behalf of the sitting United States president", Putin told NBC News.