Tsai's lawsuit says "the sole and exclusive consideration, motivation and reason" for giving the ring to Bush was their "contemplated marriage." He says he and Bush agreed she would return the ring if they decided not to marry.
The engagement was called off on Jan. 23, Tsai's papers say, and he asked for the ring back, but Bush, formerly married to the president's younger brother, Neil Bush, has refused to return it.
"Defendant (Sharon Bush) has failed and refused, despite due demand, to return the ring to plaintiff (Tsai)," his court papers say.
Tsai's lawsuit, filed Monday in Manhattan's state Supreme Court, asks for the ring's "fair and reasonable replacement value" of $434,000.
Bush's lawyer, David Berg, said Tuesday he was aware of the ring but not of Tsai's lawsuit. He said he had no further comment.
Tsai and Bush each have homes on Manhattan's Upper East Side.
Sharon and Neil Bush, 53, divorced in April 2003 after 23 years of marriage and three children, including model Lauren Bush. During divorce proceedings, Neil Bush said he admitted to his wife he had been seeing Maria Andrews, once a volunteer for former first lady Barbara Bush. He described his marriage then as "broken" and "loveless."
Neil Bush began seeing Andrews in 2002. The two married in March 2004 in a small ceremony attended by former President George H.W. Bush and Barbara Bush.
Tsai, born in Shanghai, China, began his investment career in 1951 as a security analyst at Bache & Co. Since then he has bought, sold and run several companies. He is a director at Apollo Investment Corp. in New York.
