The chairman of Taiwan's ruling Nationalist party is visiting the Chinese mainland and says that further cooperation between the two sides is of utmost importance.

Eric Chu is expected to meet with President Xi Jinping on Monday as the former bitter enemies continue their two decade-old rapprochement.

He said they must have a "positive attitude to welcome an era of cross-strait cooperation."

Chu spoke at the opening ceremony of a cross-strait economic and cultural forum in Shanghai attended by representatives from small and medium-size businesses.

He is the third Nationalist chairman to visit the mainland and the first since 2009.

Beijing considers Taiwan to be Chinese territory to be brought under its control by force if necessary, although it ruled the island for just four of the past 110 years.