The US Senate has approved building fences along strategic parts of the US-Mexico border and barring illegal immigrants with criminal records from legal residency.
In another crucial bi-partisan vote that enhanced chances of passage next week, the Senate, by 66-33, defeated a bid led by Louisiana Republican David Vitter to cut out parts of the bill that create a path for illegal immigrants to get legal status.
The legislation, generally backed by President Bush, would tighten border security while creating a guest-worker programme and a path toward citizenship for many of the estimated 11 million to 12 million illegal immigrants.
The Senate by an 83-16 vote backed fences on 595 kilometres of the 3,200 kilometres border, focusing on areas where there is a high volume of illegal crossings. About 112 kilometres of fence already exist, although sections are in disrepair, and the Department of Homeland Security already has plans to build the rest.
The 99-0 Senate vote to block felons and people with three misdemeanour convictions from legal residence or citizenship came after a compromise that would allow illegal immigrants who had ignored deportation orders to stay in the United States if their departures would cause "extreme hardship" to family members in the country legally.
Even if the fragile Senate coalition holds together, it faces extremely tough negotiations with the US House of Representatives, which passed a tougher and narrower bill focusing only on border security and enforcement.
The issue has proven divisive for Mr Bush's Republican Party in a congressional election year when it wants to thwart challenges to its control of the House and Senate.
Many conservatives oppose any hint of an amnesty for illegals, while business groups want a pool of foreign workers, and Hispanic groups are flexing political muscle demanding legalisation.
About 1,000 immigrant rights supporters rallied in Washington yesterday in favour of immigration reform.