By Faith Hung and Paul Carsten

TAIPEI/BEIJING (Reuters) - Taiwan's opposition Kuomintang (KMT) party is pushing for peace with mainland China and holds out the possibility of a peace pact, the party's chairwoman told Chinese leader Xi Jinping on Tuesday, the party said.

Xi, general secretary of the Communist Party and China's president, met a delegation led by KMT chairwoman Hung Hsiu-Chu at Beijing's Great Hall of the People, the Xinhua news agency reported.

Taiwan, which relies on the United States for arms sales, has ruled itself as a rival to China since the end of a Chinese civil war in 1949. Beijing sees the island as a renegade province that must be reunited with the mainland, by force if necessary.

Hung, once a presidential candidate, said the KMT would play an active role in pushing for the "institutionalisation" of peaceful relations between the two sides and for the possibility of a peace pact, the KMT said in a statement released in Taiwan.

Relations between the mainland and Taiwan have deteriorated since the island's pro-independence Democratic Progressive Party (DPP) took power in May after winning an election.

In his meeting with Hung, the Chinese president said Taiwan's changing politics would not affect the meaning of the 'One China' principle, China's state radio said.

China's position on this issue will not waver or be blurred in the slightest, the broadcaster cited Xi as saying.

Beijing cut an official communication mechanism with Taiwan in June, after Taiwan's President Tsai Ing-wen of the DPP refused to commit to the "One China" principle that Taiwan is part of China.

In response to comments made in the meeting, Taiwan's China policy-making body reiterated its desire for China to resume talks.

"A peaceful development of cross-strait ties is the responsibility of both sides... We should both make mutual gestures of goodwill, to resolve our differences via constructive dialogue," said the Mainland Affairs Council in a statement.

The previous KMT administration had agreed to recognize the "1992 consensus", which states that there is only one China, with each side having its own interpretation of what that means.

The KMT, a bitter rival of Beijing for decades, has in recent years been seen as more pragmatic about ties based on economic cooperation.

Communist forces defeated the KMT in the civil war, and the KMT forces fled to the island.

(Additional reporting by Monitoring Desk in Beijing; Editing by Clarence Fernandez and Hugh Lawson)