President Obama has been calling Republican and Democratic senators on Tuesday to discuss the gun-control vote, a White House official said.
Obama is expected to reach out to between half a dozen to a dozen senators in all, the official said.
The White House would not provide the call list, so it's unclear whether Obama is reaching out to Republican senators who have promised to filibuster gun-control legislation.
One of the seantors to speak with Obama was Sen. Mark KirkMark KirkThe Hill's 12:30 Report Trump, judges on collision course GOP senator: Don't link Planned Parenthood to ObamaCare repeal MORE (R-Ill.). Kirk wrote on Twitter that he "had a good conversation" with the president about North Korea and background checks for gun sales.
Speaking to reporters on Tuesday, White House press secretary Jay Carney said it would be "appalling" if some Republicans filibustered legislation supported by a majority of Americans.
"Have the courage of your convictions and allow a vote and vote no," Carney said. "If you want to vote no, vote no. How can you tell the families of Newtown victims, some of whom are here today, trying to urge members of the Senate to pass, or at least vote on these commonsense measures, that the memory of their children doesn't at least deserve that. I can even imagine that conversation."
The White House spokesman went on to say, if "senators don't have the guts to go on the record to vote how they feel on this issue ... that would be a shame, and that would be a disservice to their constituents and the 90 percent of the American people who want this passed."
— This story was updated at 5:07 p.m.