China and European Union candidate Serbia have signed an agreement to build a "shared future," making the Balkan country the first in Europe to agree on such a document with Beijing.

After meeting in Belgrade, Chinese leader Xi Jinping and Serbian President Vucic announced they would "deepen and elevate the comprehensive strategic partnership between China and Serbia," and "build a new era of a community with a shared future between China and Serbia."

It was not immediately clear what a "shared future" meant, but it is unlikely to be met with approval from the EU.

Ahead of the meeting, both sides expressed optimism that Xi's visit would further boost the "ironclad" friendly relations between China and the Balkan country.

Xi arrived in Serbia to a warm welcome on Tuesday evening from France, where he had a high-stakes state visit dominated by trade disputes and Russia's war in Ukraine.

People gather near the meeting between Chinese President Xi Jinping and Serbian President Aleksandar Vucic in Belgrade. –  Reuters

Thousands of people chanting "China-Serbia" and waving flags were bused in from across Serbia to attend a welcoming ceremony for Xi on Wednesday in front of the Serbia Palace, in the new part of Belgrade where the talks were held.

Serbia's populist president addressed the crowd from a balcony, calling Xi an "ironclad" friend. He said his visit to Serbia was "historic" because it opened the path for even closer ties.

"We are writing history today, although it doesn't seem so to many," Vucic said.

"We thank President Xi. He hasn't come to Europe in five years and he has again chosen our little Serbia."

At the start of the official meeting on Wednesday, Xi said "we are first-hand witnesses that the Serbian people view Chinese people as ironclad best friends."

"This is truly two-sided and truthful friendship ... I truly hail this and it really made an extremely deep impression on me," Xi said, according to the state RTS television.

Xi is traveling to Hungary later on Wednesday. Like Serbia, Hungary is seen as one of China's more friendly partners in Europe.

Signs of pro-China sentiments were visible throughout the Serbian capital. A huge Chinese flag was placed on a skyscraper along a roadway leading into the city from the airport. Smaller Chinese and Serbian flags could be seen downtown and along a highway.

Chinese President Xi Jinping attends a meeting with Serbian President Aleksandar Vucic at the Palace of Serbia in Belgrade. – Reuters

China has poured billions of dollars into Serbia in investment and loans, particularly in mining and infrastructure. The two countries signed an agreement on a strategic partnership in 2016 and a free trade agreement last year.

Some of those agreements, such as the free trade pact, are not in line with EU conditions for membership. Although Serbia formally wants to join the 27-nation bloc, it has been steadily drifting away from that path.

Serbia, a landlocked nation in the heart of the Balkans, has been a key country in China's Belt and Road initiative designed to increase Beijing's influence in Europe through economic investment. Critics say it could serve as a Chinese Trojan horse and gateway to Europe.

Xi arrived in Serbia on a symbolic date — the 25th anniversary of the bombing of the Chinese Embassy in Belgrade by U.S. jets during NATO's air war over Kosovo, when three Chinese citizens were killed.

A woman holds the Chinese and Serbian flags as she waits for the arrival of Chinese President Xi Jinping in Belgrade. – AP

The incident has helped forge close political ties between China and Serbia.

Chinese companies run Serbia's biggest copper mine and a steel mill, and are also building scores of roads and highways across the country, along with a railway toward northern neighbor Hungary.

In 2014, Hungary and Serbia concluded an agreement with Beijing to modernize the railway between their capitals of Budapest and Belgrade, part of a Belt and Road plan to link up with the Chinese-controlled port of Piraeus in Greece to the south, an entry point for Chinese goods to Central and Eastern Europe.

The more than $2 billion project is expected to be completed in 2026, after numerous delays.

In 2022, shortly after the Russian invasion of Ukraine, Serbia took semi-secret delivery of a sophisticated Chinese anti-aircraft system flown in on Chinese Air Force Y-20 transport planes.

The arms delivery over the territory of at least two NATO member states, Turkey and Bulgaria, was seen by experts as a demonstration of China's growing global reach.