– The Associated Press

WASHINGTON – Bickering across a deep divide, supporters of immigration legislation pushed back hard Wednesday against Republican demands for tougher border security measures before millions living illegally in the country could take the first steps toward U.S. citizenship.

Even modest changes were snared in the political crossfire that erupted on the first full day of debate on the measure, as the two sides failed to agree on terms for voting on seemingly non-controversial proposals such as granting tribal officials a place on a Border Oversight Task Force.

Public polling shows general support both for tougher border security and for allowing those living in the United States to gain citizenship after meeting certain legal, financial and other conditions. On an issue as contentious as immigration, that made the intersection of the two a fertile ground for dispute.

As drafted, the legislation “authorizes a permanent legalization program for illegal immigrants regardless of whether the Mexican border is ever secured,” said Sen. John Cornyn, R-Texas. The Senate’s second-ranking leader also wants other measures implemented, including a biometric system to check everyone departing the country at a sea or airport, that Sen. Chuck Schumer, D-N.Y., said could take a quarter-century to take effect fully.

“We cannot, should not and will not tell those who have waited in the shadows for so long that they should wait for 25 years,” said Schumer, who was part of a bipartisan “Gang of Eight” group of senators who negotiated the bill’s basic provisions and then protected it from major changes in the Judiciary Committee last month.

In addition to taking steps to secure the border and begin a legalization process for millions, the White House-backed legislation would increase the number of visas for highly skilled workers, create a new program for the lesser-skilled to work in the United States and overturn a family-based system for legal immigration that has been in place for decades.

Senate Majority Leader Harry Reid, D-Nev., has said he wants a final vote on the measure before July 4.

Across the Capitol, House Speaker John Boehner, R-Ohio, says he hopes immigration legislation can move through committee by then, and be on the floor sometime in July.

While the obstacles to a final agreement are daunting, the Senate bill has support from both business and organized labor.