WASHINGTON — Months after the collapse of a sweeping immigration overhaul, a top Senate Democrat plans to push for a smaller measure that could give tens of thousands of undocumented high school and college students a shot at legalization.

The legislation, known as the Dream Act, could give students who were brought to the United States before they were 16 a chance for residency if they graduate from high school, stay out of trouble and complete at least two years of college or enlist in the military.

Immigration advocates say the legislation, which Senate Majority Whip Dick Durbin, D-Ill., hopes to introduce as soon as next week, is the best chance for students like brothers Juan and Alex Gomez, who came to the United States as infants, were educated in Miami-Dade public schools, and now are fighting orders of deportation to Colombia.

But opponents already are gearing up, hoping to torpedo the measure, which they consider "piecemeal amnesty."

Sen. Jeff Sessions, R-Ala., who helped derail the immigration bill, this week sent out a letter to his colleagues, warning that "a conservative estimate suggests that at least 1 million illegal aliens will qualify" for the provision.

Though Sessions' opposition is not unexpected, it represents one of the considerable hurdles the legislation has faced since it was introduced in 2001. The climate for passage may be particularly tough this year, with anti-immigration advocates emboldened by the defeat of the larger immigration bill, which had the backing of President Bush and Florida Sen. Mel Martinez, the general chairman of the Republican National Committee.

Durbin acknowledges the uphill battle but said he has bipartisan backing and is working both sides to garner more support.