A Supreme Court decision could come within hours or days.
Correspondents suggest that new voting now seems likely as part of a resolution to the crisis, but it is not clear whether in the form of a repeat of the second-round runoff, as Yushchenko has demanded, or a whole new election, as outgoing President Leonid Kuchma has reportedly proposed.
Meanwhile, Interfax-Ukraine reported today that President Kuchma has flown to Moscow for a meeting with Russian President Vladimir Putin, who appeared to favor Yanukovych in the run-up to voting.
Kuchma's press service said he will hold "political consultations" with Putin during his visit.
Moscow has exchanged verbal barbs with many in the West over foreign governments' handling of the Ukrainian vote and its popular and political fallout.
Yushchenko yesterday called on his supporters to continue street protests. But it was unclear today whether protesters were complying with Yushchenko's request that they allow employees access to government and other key buildings, a concession that emerged from yesterday's negotiations.
[Click here for more RFE/RL coverage of Ukraine's disputed presidential election.]