Chinese President Xi Jinping said Wednesday that "external interference" would not stop Beijing from unifying with Taiwan, as he met the self-ruled island's former leader in a rare display of cross-strait dialogue.

Taiwan's ex-president Ma Ying-jeou is in China as part of what he has called a "journey of peace" to calm tensions with Beijing, which claims the island as its own territory and has never renounced the use of force to bring it under its control.

Xi welcomed a delegation headed by Ma to Beijing on Wednesday afternoon, Chinese and Taiwanese media reported, in a rare meeting between current or former leaders in Beijing and Taipei, and the first since a landmark summit between the two men in 2015 when Ma was still in office.

"The Chinese nation has written the indivisible history of both sides of the Taiwan Strait and engraved the fact that our compatriots... are connected by blood," Xi said in footage of the meeting broadcast by Taiwan's TVBS News.

"There is no force that can separate us... Differences in systems cannot change the objective fact that we belong to one nation and one people," Xi was shown telling Ma across a glossy table in an ornate reception room in the capital.

"External interference cannot stop the historic cause of our reunion," Xi said.

Ma has been leading a delegation of 20 Taiwanese students and has visited technology firms, universities and historical sites since arriving in China last week.

In his remarks to Xi, Ma said "young people on both sides of the Taiwan Strait represent the future of the Chinese nation".

"If war were to break out between the two sides, it would be an unbearable burden for the Chinese nation," he said.

"Chinese people on both sides of the strait absolutely have ample wisdom to peacefully handle disputes and avoid conflicts," said Ma, adding that they should also "oppose Taiwan independence".

'Fan of China'

Ma served two terms as Taiwan's leader between 2008 and 2016, representing the Kuomintang (KMT) party, long more receptive to Beijing.

He oversaw an improvement in cross-strait ties and held symbolic talks nine years ago with Xi in Singapore, the first meeting between the political leaders of China and Taiwan since the end of the Chinese civil war in 1949.

But relations have plummeted since the 2016 election of Ma's successor Tsai Ing-wen, who rejects Beijing's claims.

Since then, China has ratcheted up diplomatic and military pressure, and has refused to rule out using force to "unify" with Taiwan.

The election in January of Tsai's deputy Lai Ching-te stands to worsen cross-strait ties, with Beijing having denounced him as a "dangerous separatist".

A spokesperson for Lai's Democratic Progressive Party said Ma's visit would "have a great impact on Taiwan" if he was speaking on behalf of the KMT.

"So far, we have not seen the KMT come forward to endorse or approve Ma's visit, so we are very curious about (their) attitude (towards it)," Wu Cheng said.

Ma "seems to be a fan of China and likes to go to China", Wu said.

The Taiwan Foreign Ministry took a harder tone, saying "Beijing authorities" had "taken advantage of this meeting to indulge in unbridled propaganda regarding their claims to Taiwan".

"If China really wants to show goodwill towards Taiwan, it must immediately cease all acts of coercion... and, on the basis of reciprocity, resume dialogue with the democratically elected government," it said in a statement.

Worsening ties

Lai has said he hopes to maintain the status quo with China.

Chinese warplanes and ships maintain a near-daily presence around the island, as Beijing has ramped up military pressure against Taipei using what experts say are "grey zone" actions -- tactics that stop short of outright acts of war.

Taiwan was among the issues discussed by US President Joe Biden and China's Xi in a call last week.

The White House said Biden pressed Xi to ensure "peace and stability" across the Taiwan Strait ahead of Lai's inauguration in May.

Xi told Biden that Taiwan remains "an uncrossable red line" for Beijing, according to Chinese state media.