WASHINGTON -- The White House says it is "encouraged" by recent progress on efforts to overhaul immigration.

White House spokesman Jay Carney cited positive comments from a bipartisan cast of senators over the weekend. He would not comment on cautionary remarks from Sen. Marco Rubio, R-Fla., a key participant in the Senate negotiations.

A proposal being assembled by a bipartisan group of eight senators would provide a new class of worker visas for low-skilled workers, secure the border, crack down on employers, improve legal immigration and create a 13-year pathway to citizenship for the millions of illegal immigrants already here. Labor and business leaders have agreed on a framework for the plan.

Carney said the work by the senators reflects President Barack Obama's principles for changing immigration law. He added, "The process continues and is not finished."