White House spokesman Scott McClellan said Bush's aim was "to underscore his personal support for the [wives'] efforts to seek justice for the disappeared, as well as for all those who seek to return freedom to Belarus.
Bush joined a meeting of his national security adviser, Stephen Hadley, with Iryna Krasouskaya and Svyatlana Zavadskaya.
Anatol Krasouski, a businessman who had criticized Belarusian President Alyaksandr Lukashenka, vanished without trace in September 1999.
Dzmitry Zavadski, a cameraman in Minsk for Russian broadcaster ORT, disappeared on his way to pick up his colleague Pavel Sheremet from the Minsk airport on 7 July 2000.
McClellan said the United States believes that the Belarus authorities are to blame for the two men's disappearance.
Belarus Votes 2006
MEET THE CANDIDATES: Read brief biographies of the four candidates in the March 19 election.