China's efforts over the past decade to become a more cooperative player in world affairs and improve relations with Washington could help position it to take over Taiwan in the long term by building up international support for a takeover, a leading China expert in Washington warned on Thursday.

Bates Gill, an academic at the Center for Strategic and International Studies, said that China would prefer to absorb Taiwan through diplomacy and economics, but warned that China's aggressive military buildup indicates that Beijing is still preparing for military action if needed.

He also spoke of a "very important constituency in Taiwan" that would welcome such a unification.

Gill made his comments in a presentation introducing his new book, Rising Star: China's New Security Diplomacy and its Implications for the United States, which details a new Chinese diplomatic effort begun in 1998-1999 to interact with other countries in world affairs and build a set of interests "convergent with US interests."

Describing Beijing's new policy toward Taiwan as "a combination of intensified carrots and intensified sticks," he said it was part of its overall new diplomatic strategy seeking "to create a space with regard to Taiwan so that it can realize national reunification, preferably through diplomatic and economic means."

At the same time, "under the rubric or umbrella of a more benign and constructive set of policies," Beijing is moving forward aggressively to build its military "to use that option if it needs to," he said.

For someone in Taiwan, Gill said, "I would breathe a sigh of relief that China's threat of a military solution is probably drastically diminished," compared with earlier years. But the reaction in Taiwan would ultimately depend on "who you are in Taiwan today."

"There are those who are going to breathe a sigh of relief because the new security diplomacy probably argues in favor of a peaceful environment across the Strait in the near to medium term," Gill said.

"But there are those who are not going to be very happy because it also argues for China increasingly positioning itself with its neighbors, with the United States, and even with a very important constituency in Taiwan, positioning itself in a way that is going to help it realize its goal of unification over the longer term," he said.

Gill did not name the Taiwanese constituency he mentioned, but appeared to be referring to the pan-blue camp.