Chinese President Xi Jinping has revealed 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, in a rare meeting between the leaders, which is the first since a landmark summit between the two men in 2015 when Ma was still in office.

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 that young people on both sides of the Taiwan Strait represent the future of the Chinese nation.