Ukraine's opposition is set to present its demands for the release of jailed protesters and cutting the president's powers, while the EU's foreign policy chief is returning to Kiev in a fresh bid to end the two-month crisis.
President Viktor Yanukovych has blasted the mass protests against his rule as "extremism", but the European Union and United States will mull economic aid to help end the country's political crisis.
In a boost to the opposition, which is due to press its fresh demands in a parliament session Tuesday, the EU and US linked any possible economic aid to democratic reforms and a new government.
EU foreign policy chief Catherine Ashton returns to Kiev on Tuesday in a fresh bid to end the standoff, triggered when Ukraine walked away from a political and trade deal with the EU in favour of closer ties with Soviet-era master Moscow.
US Assistant Secretary of State Victoria Nuland is also due to visit Ukraine this week to keep the pressure on Yanukovych.
Returning to work after four days of sick leave on Monday, Yanukovych slammed the anti-government movement as "radicalism and incitement to hatred behind which there is a struggle for power".
He also appeared to link militants to Nazis, calling for "a community of wholesome people without the Nazism, racism and xenophobia that remind us of the terrible lessons of history" in his first public comments since Thursday.
The mass protests have set off sparks between Russia and the West and claimed the lives of at least two protesters and two policemen.
Thousands remain camped out on Kiev's Independence Square and in occupied buildings in the capital.
Ashton's spokeswoman Maja Kocijancic said the EU and its foreign partners were talking about "what we can do to help support the Ukrainian economy" but stressed any aid would be linked to political reforms or the naming of a new government.
State Department spokeswoman Jen Psaki said the talks were "at a very preliminary stage".
"We are consulting with the EU ... and other partners about the support Ukraine may need after a new technical government is formed as the country gets back on the path to economic health through the IMF," she said.
Asked to comment, Foreign Minister Leonid Kozhara said in Kiev: "Nobody has discussed this with me."
Opposition leader Arseniy Yatsenyuk has asked for a "Marshall Plan" - a reference to US aid for Europe after World War II - and said the minimum required was the $US15 billion ($A17.2 billion) that Russia has promised Ukraine in a bailout that is now on hold.
