Chinese President Xi Jinping urged Shanghai Cooperation Organisation members to leverage their "mega-scale market" on Monday, while unveiling his ambition for a new global security and economic order that poses a challenge to the United States.

The Shanghai Cooperation Organisation (SCO) has set a model for a new type of international relations, Xi said in opening remarks addressing more than 20 world leaders at a two-day summit held in northern China's port city Tianjin.

"We should advocate for equal and orderly multipolarisation of the world, inclusive economic globalisation and promote the construction of a more just and equitable global governance system," he said.

China will provide 2 billion yuan ($280 million) of free aid to member states this year and a further 10 billion yuan of loans to a SCO banking consortium, he added.

"We must take advantage of the mega-scale market... to improve the level of trade and investment facilitation," said Xi, urging the bloc to boost cooperation in fields including energy, infrastructure, science and technology, and artificial intelligence.

Russia's Vladimir Putin, Indian Prime Minister Narendra Modi and other leaders from Central Asia, the Middle East, South Asia and Southeast Asia attended the opening ceremony in a major show of Global South solidarity.

The security-focused bloc, which began as a group of six Eurasian nations, has expanded to 10 permanent members and 16 dialogue and observer countries in recent years.

Xi also called on organisation partners to "oppose Cold War mentality and bloc confrontation" and to support multilateral trade systems, an apparent dig at U.S. President Donald Trump's tariff war which has disproportionately affected developing economies such as India, whose exports were hit with a 50% levy last week.

United Nations Secretary-General Antonio Guterres said China played a "fundamental" role in upholding global multilateralism on Sunday.

Analysts say China will use this year's largest-ever summit to demonstrate an alternative vision of global governance to the American-led international order at a time of erratic policymaking, a U.S. retreat from multilateral organisations and geopolitical flux.

Beijing has also used the summit as an opportunity to mend ties with New Delhi.

Modi, who is in China on his first visit in seven years, and Xi both agreed on Sunday that their countries are development partners, not rivals, and discussed ways to improve trade ties amid the global tariff uncertainty.