The mainland's chief negotiator Chen Deming would be deeply regretful if a cross-Straits service trade pact is not passed in Taiwan.

Speaking at a forum on Sunday, Chen, president of the Chinese mainland-based Association for Relations Across the Taiwan Straits (ARATS), said the trade pact could boost Taiwan's economy as the economies of the mainland and the island are highly complimentary.

As a follow-up to the 2010 Economic Cooperation Framework Agreement, the trade pact aims to open up 80 of the mainland's service sectors to Taiwan and 64 Taiwan sectors to the mainland.

The service sector contributed for more than 70 percent of Taiwan's GDP, whereas the mainland has a strong manufacturing sector and records a trade deficit in its service industry, according to Chen.

Signed in June, the trade pact spent over five months waiting to be ratified in Taiwan's legislative authority. Legislators of the ruling Kuomintang blamed the pro-independence opposition Democratic Progressive Party (DPP) for persistently blocking the review process.

The pact was sent to the legislative session on March 17 after the KMT decided that the clause-by-clause review had been completed. The decision sparked protests from the DPP and students, leading to accusations of "undemocratic" tactics used to speed up ratification of the pact.

Taiwan leader Ma Ying-jeou said on Saturday evening that he agreed to a clause-by-clause review and vote on the trade pact but is against withdrawal of the agreement.