WASHINGTON (AP) — A key Democratic senator says a deal on reforming immigration could stall over how to define border security and a path to citizenship for illegal immigrants.

Sen. Charles Schumer of New York, a leader in bipartisan negotiations, says another major obstacle is reaching agreement on a guest worker program — something business wants and organized labor has concerns about.

Schumer and the other seven senators who proposed an immigration bill blueprint this week want assurances on border security before a path to citizenship can begin. Republicans say they can’t support a bill without that.

The Senate working group has been meeting this week to discuss how to define border security. Schumer says lawmakers envision allowing the Homeland Security secretary final say on whether border security criteria have been met.