Senate leaders said on Monday that the treaty would not be brought to floor until the verification issues were resolved.
But resolving nettlesome verification issues over the new treaty is a primary concern.
Opposition in the Senate to ratification of the treaty is likely to focus on verification issues.
The subject of intermediate testing measures is not to be taken up until difficult verification issues over the existing treaties are first resolved.
But some important verification issues still remain to be resolved on verification.
But important verification issues reportedly remained unresolved after two days of high-level talks here.
Arms control experts consider the verification issue to be one of two major points that could block an agreement on medium-range missiles in Europe.
Washington made new proposals on the verification issue Tuesday.
Even though the two sides have worked out many differences, officials say that verification issues were deferred during the talks this week.
Some of the verification issues have been debated within the Administration before.