Climate change and Covid are at the top of the agenda as world leaders gather in Italy.
It is the first time the G20 leaders have met in person since the outbreak began.
China's Xi Jinping and Russia's Vladimir Putin, on the other hand, will not be in Rome for the summit, instead of appearing via video link.
The meeting takes place in the midst of increasingly dire warnings about the future if immediate action to reduce emissions is not taken.
The group, which includes 19 countries and the European Union, is estimated to account for 80 percent of global emissions.
Speaking ahead of the two-day summit, UK Prime Minister Boris Johnson warned that failure to act would result in "our civilization" regressing, condemning "future generations to a life far less agreeable than our own."
He did, however, acknowledge that neither the G20 meeting nor the upcoming COP26 summit in Glasgow, which begins on Monday, will be able to stop global warming, saying that "the best we can hope for is to slow the increase."
According to Reuters, a draught communiqué outlines the G20's promise to work toward limiting temperature rises to 1.5 degrees Celsius (2.7 degrees Fahrenheit), but no legally binding agreement will be reached.
According to Reuters, the draught also promises to take "concrete measures" to stop illegal logging, mining, and wildlife trades.
During the summit, Mr. Johnson is expected to address coronavirus vaccine inequality, telling his fellow leaders that "the pace of recovery will depend on how quickly we can overcome Covid," with the first priority being "the rapid, equitable, and global distribution of vaccines."
Over six billion Covid vaccine doses have been administered globally. However, a letter from more than 160 former world leaders and global figures to Italian Prime Minister Mario Draghi, who is hosting the G20, stated that only 2% of people in low-income countries have received a jab.
Mr. Draghi described the disparity as "morally unacceptable" on Saturday. He urged fellow leaders to "do everything we can" to vaccinate 70% of the world's population by the middle of next year.
Meanwhile, US Vice President Joe Biden will press countries to increase energy production in the face of skyrocketing prices, as well as discuss a plan to prevent future pandemics. He will also meet with Mr. Johnson, France's Emmanuel Macron, and Germany's outgoing Chancellor Angela Merkel to discuss reviving the Iran nuclear deal.
The group is also expected to support a global minimum corporate tax rate of at least 15%, which is supported by 140 countries worldwide. The draught communiqué anticipates that it will be in place by 2023.