[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2009/images/02/05/art.collins.gi.jpg caption="Collins is among a bipartisan group of senators seeking to rework the stimulus bill."](CNN) - The bipartisan meeting of senators looking to reach a deal on the stimulus bill ended their second meeting Thursday afternoon sounding significantly less optimistic than they had earlier in the day.
Democrat Ben Nelson of Nebraska, Republican Susan Collins of Maine, and others said it was proving tough to reach the right balance on spending - cutting some programs while adding funds for infrastructure projects.
Independent Sen. Joe Lieberman said they're trying to find the "sweet spot" on that mix.
Still, two Democratic senators said they have found general agreement to cut some $100 billion from the bill, a number they have reached as they have added cuts throughout the day.
When the meeting broke up, Republicans were going to talk amongst themselves, and Democrat Ben Nelson went to update his leadership. Nelson says he's also in touch with the White House.
Meanwhile, Democratic leader Harry Reid issued a public warning to the senators in that room not to overreach.
"They cannot hold the president of the United States hostage," he said. "If they want to work constructively, we will work with them. The president has instructed me to work with them if it's going to help the legislation. But if they think they are going to rewrite this bill and Barack Obama's going to walk away from what he has been trying to do for the American people, they've got another thought coming."
When asked about those comments, Collins became visibly annoyed.
"I would say to the majority leader his success depends upon the success of this group," the Maine Republican said.