Mr Bush was speaking during talks with his Mexican counterpart, Vicente Fox, at a two-day summit in Cancun, also involving Canada.
Mr Bush said he was not in favour of allowing illegal immigrants to be put on a fast-track to US citizenship.
But he promised to try to push through legislation on a work-permit system.
Mr Bush did not give a timetable for reform, which faces what he called a cumbersome process in the US Congress, where hardline conservatives are strongly opposed to it.
Source: BBC News
