Senate Majority Leader Harry Reid, D-Nev., on Monday delayed a key procedural vote on legislation to extend unemployment benefits for 1.3 million Americans as Democrats and Republicans continued negotiations on a bipartisan accord.

The measure to aid the long-term jobless still needs about a half-dozen Republican votes to clear a 60-vote threshold and advance to a final vote. But Republicans are withholding those votes to pressure Reid to allow votes on Republican amendments to the bill, a demand Reid on Friday hinted he could accept.

Sen. Dean Heller, R-Nev., the chief Republican negotiator, confirmed that progress was being made toward a bipartisan agreement on the extension. Heller said any agreement would have to allow votes on GOP amendments and offset the cost with budget cuts.

"There are multiple issues here and that's why the negotiations are taking so long," Heller told reporters Monday evening. "I'm pretty optimistic."

Republicans' chief demand is that the $6.5 billion price tag of the benefits extension be offset by spending cuts elsewhere in the budget. Democrats are resisting additional budget cuts, noting that lawmakers approved five benefits extensions under President George W. Bush without such offsets.

The GOP also wants to limit any extension of benefits to the long-term jobless to three months, another proposal Democrats are resisting.

Reid said on the Senate floor Monday that differences between the two sides remain. But, he added, "that doesn’t mean that we can’t work something out.”

A vote on the extension is now scheduled for Tuesday afternoon, but could be delayed further if the two sides fail to reach a compromise by then.