WASHINGTON (AP) — Struggling to salvage a massive surveillance program, President Barack Obama faced congressional critics of the National Security Agency’s collection of Americans’ telephone records Thursday as snowballing concerns made new limitations on the intelligence effort appear increasingly likely.

Obama and Vice President Joe Biden joined lawmakers on both sides of the issue for an Oval Office meeting designed to stem the bleeding of public support and show Obama was serious about engaging. Among the participants were the NSA’s most vigorous congressional supporters — the top Democrats and Republicans in the House and Senate intelligence panels — alongside its most stern critics, including Democratic Sens. Ron Wyden of Oregon and Mark Udall of Colorado.