The U.S. President Joe Biden said that Senate negotiators trying to work out an agreement on moderate measures to combat gun violence are still “slightly optimistic.”

He made the comment after talking several times with Democratic Senator Chris Murphy, who is negotiating.

Tens of thousands of demonstrators rallied in Washington, D.C., and across the country on Saturday, calling on lawmakers to pass legislation aimed at eradicating gun violence.

Biden, who earlier this month called on Congress to ban assault weapons, expand background checks on gun buyers and introduce other gun control measures, said he supported Saturday’s protests.