"You have much to lose by not complying with conditions of release," Turnoff said at a hearing to Castroneves, who nodded vigorously in agreement.
Castroneves, who also won the 2007 TV "Dancing with the Stars" competition, is charged with conspiracy and tax evasion for allegedly dodging U.S. taxes on about $5.5 million in income using offshore accounts. He has pleaded not guilty and is free on $10 million bail.
Turnoff, in a wry reference to Castroneves' dancing career, said he would have to "tango with the U.S. Marshals" if he didn't show up for court.
The judge initially prohibited Castroneves from traveling outside the continental U.S. for races or other work but agreed Friday to modify those conditions for the Oct. 26 event in Brisbane, Australia. Castroneves attorney David Garvin said there was zero chance he would flee prosecution, especially to a Brazil he left in 1996.
"Unless he's planning to go to the Amazon, there's no place to go in Brazil," Garvin said.
Assistant U.S. Attorney Matt Axelrod, however, said Castroneves has $15 million in an account in the Netherlands and access to millions more in Brazil, where he owns Burger King restaurants and a car dealership. Facing a potential prison term of up to five years, Axelrod said the 33-year-old driver had ample reason to run.
"His career's at risk either way," Axelrod said. "He has extensive ties there."
Turnoff did give prosecutors until close of business Tuesday to appeal his order to another federal judge, but the U.S. attorney's office later Friday said no appeal was planned.
Garvin also said Castroneves intends to pay the Internal Revenue Service about $5 million in taxes after his offshore "deferred royalty contract" expires on Dec. 31. That account is central to the criminal case, which alleges that Castroneves, his sister and a Michigan lawyer created fraudulently to evade taxes between 1999-2004.
All have pleaded not guilty.