KIEV, Dec. 15 - The European Union said on Sunday it was halting work on a landmark trade and political pact with Ukraine, hardening their rift even as tens of thousands took to the streets of Kiev urging President Viktor Yanukovych to mend ties with Brussels.

EU enlargement chief Stefan Fuele said on Twitter the words and deeds of Yanukovych and his government on the deal were "further and further apart,” Reuters reported.

His announcement came as 200,000 people braved sub-zero temperatures in Kiev to rally for the fourth weekend in a row against Yanukovych's decision not to sign the EU pact at a summit last month and concentrate instead on closer ties with Russia.

The EU had kept its offer on the table but Fuele said on Sunday the Ukrainian government's subsequent arguments on the terms of the deal had "no grounds in reality". "Work on hold," he added.

Fuele's words suggested the EU has lost patience with Kiev's demands for financial aid and was irritated at the way the bloc was being forced to take part in a 'bidding war' with Russia over Ukraine.

The focus was now on a visit Yanukovych is due to make to Moscow next Tuesday to tie up trade agreements with the Kremlin to help the distressed Ukrainian economy.

The opposition fears he may take the first steps towards joining a Moscow-led customs union, together with Belarus and Kazakhstan, which they see as an attempt by President Vladimir Putin to re-create the Soviet Union.

"He might as well stay in Moscow and not come back to Kiev if a customs union agreement is signed," declared an opposition leader and former economy minister Arseniy Yatseniuk. "We'll give him a really warm welcome if he sells out Ukraine."

"The Kremlin wants to take its revenge on Ukraine, divide Ukraine and drown it in blood," said Oleh Tiahnybok, the leader of the nationalist Svoboda party. "We forbid this president to sign anything in Moscow that contradicts the interests of the Ukrainian state."

Protesters called for another mass rally on Tuesday to monitor Yanukovych's trip to Moscow. Prime Minister Mykola Azarov said late on Sunday he expected a deal on lower prices for Russian gas deliveries to Ukraine.

Yanukovych may be attempting to keep the attention of both Moscow and Brussels to strike as good a deal as possible to handle its huge debt and outstanding gas payments to Moscow. But it is a hazardous maneuver running the risk of alienating both parties.

The anti-government protesters received powerful encouragement on Sunday as U.S. Senator John McCain addressed the crowd on Kiev's Independence Square, telling them their destiny lay in Europe.

"We are here to support your just cause, the sovereign right of Ukraine to determine its own destiny freely and independently. And the destiny you seek lies in Europe," said McCain, a leading Republican voice on U.S. foreign policy. (rt/ez)