President Barack Obama said he was 'modestly optimistic' while making a statement on fiscal cliff negotiations following a meeting with Congressional leaders on December 28, 2012 in Washington, DC. - 

Lawmakers have a few more hours to cut a deal that'll avoid the fiscal cliff. President Obama hit the airwaves over the weekend to pressure Congress, warning that going over the cliff would be bad for business.

"If they say that people's taxes have gone up, which means consumer spending is going to be depressed, than obviously that's gonna have an adverse reaction in the markets," Obama told NBC.

Many issues remain unresolved. The Senate is scheduled to reconvene this morning to try to work out a deal that, if passed, would make its way to the House. House Speaker John Boehner has said he would put a Senate plan up for a vote, but it's not certain whether such a bill could pass.

If no deal is reached, payroll taxes and taxes on investments will go up starting tomorrow. The Treasury Department has warned that going over the cliff will also cause the government to reach its debt limit, a reality that's likely to upset markets if no deal is reached today.

Another possibility is that lawmakers will reach a retroactive deal sometime after tonight's deadline that would reverse the most dramatic consequences of going over the cliff. Yet market observers worry that changing tax rates might cause logistical confusion.

According to Gus Faucher at PNC Financial Services Group, "the damage from the fiscal cliff would be limited at least in the near-term" with a retroactive fix. Yet Faucher notes that even temporary cuts to certain programs, such as unemployment insurance, could impact some Americans.

Follow David Gura at @davidgura