Ukraine's opposition has called another monster rally to protest President Viktor Yanukovich's rejection of an EU trade in favour of a closer relationship with Moscow.
Opposition leaders urged a massive turnout for Sunday's rally on Independence Square where the crowd swelled to hundreds of thousands last weekend.
But tensions are expected to mount as authorities are planning a counter demonstration.
They too vowed to hold a "non-stop protest" and said they would bus thousands of Yanukovich supporters from the provinces to a park near the opposition camp.
Protesters have remained in Independence Square in the capital Kiev for more than three weeks since Yanukovich decided not to sign the EU deal.
Both US and European politicians have shown their support for the opposition's cause.
Republican Senator John McCain flew to Kiev on Saturday for meetings with Vitali Klitschko, head of the Ukrainian Democratic Alliance for Reform party (UDAR), nationalist leader Oleg Tyagnybok and Arseniy Yatsenyuk, the head of Yulia Tymoshenko's party.
He praised the protests as "an incredible show of patriotism".
President Yanukovich is under pressure to choose to align Ukraine with the West or with a Russian-led Customs Union.
He will travel to Moscow next week to meet with Russian President Vladimir Putin.