Leaders of the Group of 20 nations opened talks on Tuesday on the island of Bali, with a plea by hosts Indonesia for unity and concrete action to mend the global economy despite rifts over the war in Ukraine.

"We have no other option, collaboration is needed to save the world," Indonesian President Joko Widodo said in opening remarks, before the leaders of the world's wealthiest nations began closed-door discussions.

"G20 must be the catalyst for inclusive economic recovery. We should not divide the world into parts. We must not allow the world to fall into another cold war."

President Xi Jinping warned against the "weaponisation" of food and energy.

"We must firmly oppose politicisation, instrumentalisation and weaponisation of food and energy problems," Xi told the summit in Bali.

The G20, which includes countries ranging from Brazil to India, Saudi Arabia and Germany, accounts for more than 80 percent of the world's gross domestic product, 75 percent of international trade and 60 percent of its population.

A positive sign on the eve of the summit was a three-hour bilateral meeting between Xi and his US counterpart Joe Biden in which the two leaders pledged more frequent communications despite many differences.

Meanwhile, French President Emmanuel Macron called on China and France to unite against the war in Ukraine as he met with Xi on Tuesday on the sidelines of the G20 summit.

We must "unite forces to respond... to international crises like Russia's war in Ukraine," Macron told Xi.

Xi said as two important forces in the multipolar world – China and France, China and the EU – should adhere to the spirit of independence and autonomy, as well as openness and cooperation to boost bilateral relations. (Agencies)