In a letter to Speaker John A. Boehner, Mrs. Pelosi said the Senate's bipartisan 68-32 vote moves "our country one step closer to comprehensive immigration reform," but did not endorse the controversial bill, which offered a chance at citizenship to most illegal immigrants but also calls for spending tens of billions of dollars to add 20,000 new Border Patrol agents to the southwest.
That additional border security, which Senate Democrats accepted as the price for winning some GOP votes, has irked some House Democrats who argue it militarizes the U.S.-Mexico border.
Instead, Mrs. Pelosi urged Mr. Boehner to take a look at a broad plan being developed by a bipartisan group of seven House members, which she dubbed the "Taskforce of 7." And she said House Democrats are "ready to act in a bipartisan fashion" to get a bill done.
"If you decide to take up various elements of comprehensive immigration reform under separate votes, it is essential to remember that those key elements are interconnected and necessary for reform," Mrs. Pelosi said in her letter.
Senate Democrats, including Sen. Charles E. Schumer, chief author of that chamber's bill, have both called on Mr. Boehner to bring up their bill for a vote and predicted he will eventually have to do so, after he fails to get an agreement himself.
But Mrs. Pelosi's letter signals support may be shaky even among House Democrats.
Democrats could try to force a vote on the Senate bill by circulating a discharge petition which, if it garnered 218 signatures, would push the bill to the floor.
Republicans are meeting Wednesday afternoon for a special session to hash out their strategy on immigration.