President Xi addressed almost 30 leaders on the second day of a forum on his new Silk Road plan, a huge infrastructure project intended to revive ancient land and sea trade routes from Asia to Europe and Africa.
"Globalisation is encountering some headwinds," Xi told leaders from countries ranging from Spain to Turkey, Russia and Pakistan at a convention centre near the Great Wall on the outskirts of Beijing.
"We need to seek results through greater openness and cooperation, avoid fragmentation, refrain from setting inhibitive thresholds for cooperation or pursuing exclusive arrangements, and reject protectionism."
He compared countries to "swan and geese" that can "fly long and safely through winds and storms because they move in tandem and help each other as a team".
The Chinese leader is using the international gathering to promote his signature foreign policy project, the One Belt, One Road initiative.
At the opening of the meeting on Sunday, Xi pledged to pump an extra $124 billion into the China-bankrolled project, which involves a huge network of ports, railways, roads and industrial parks.
The China Development Bank had already earmarked $890 billion for some 900 projects.
The initiative spans 65 countries representing 60 percent of the world population and around a third of global gross domestic product.
China has defended globalisation at a time when the United States is retreating into "America First" policies on trade and foreign relations under President Donald Trump.
While some see Beijing's project as a geopolitical powerplay, Xi has insisted that the Belt and Road is open to everybody.
"In a world of growth, interdependence and challenges, no country can tackle the challenges or solve the world's problems on its own," he said as he sat next to Russian President Vladimir Putin.
Putin and other leaders, including Turkish President Recep Tayyip Erdogan, applauded the initiative, which Xi unveiled in 2013.
Watch: China president Xi decries protectionism
But in a setback to Xi's effort to gain full support, several European Union countries -- France, Germany, Estonia, Greece, Portugal and Britain -- indicated they would not sign one of the summit documents on trade.
The text on trade is one of the statements that are expected to be published at the end of the summit later Monday, along with the final communique.
A diplomat who requested anonymity told AFP the EU countries believe the text does not sufficiently address European concerns on transparency of public procurement and social and environmental standards.
Cultural dazzle for Silk Road revival
China only presented the document to negotiators last week, telling them it could no longer be reworked, according to the official.
On Sunday German Economy Minister Brigitte Zypries called for transparency to ensure that the calls for investment bids are "non-discriminatory".
"I think there is still room for improvement in this area," Zypries said.
While Greece and Britain are among the nations that refused to sign up to the document, both countries publicly praised Xi's overall project.
"In these times, when the temptation is great to respond to the crisis of globalisation by increasing isolation, and by raising walls, this initiative highlights a vision of connectivity, cooperation and dialogue across Europe and Asia but also other parts of the world," Greek Prime Minister Alexis Tsipras said on Sunday.
British finance minister Philip Hammond said London was "ready to work with all Belt and Road partner countries to make a success of this initiative".
Europeans are not the only ones voicing concerns.
India skipped the summit as it voiced displeasure at the China-Pakistan Economic Corridor, a Belt and Road project aimed at linking northwestern China to the Arabian Sea.
The route cuts through Gilgit and Baltistan in Pakistan-administered Kashmir, disputed territory that India claims is illegally occupied.