* Opposition fears president set to sign Moscow pact
* Hopes for million participants in Sunday rally
* Police want to eject protesters from key buildings
By Gareth Jones and Alissa de Carbonnel
KIEV, Dec 8 (Reuters) - Organisers hope one million protesters will turn out in Kiev on Sunday to pile more pressure on Ukraine's President Viktor Yanukovich as he seeks closer ties with Russia after dumping a trade pact with the European Union.
The rally will further heighten tension in the weeks-long standoff between the Yanukovich government and its opponents.
The confrontation has raised fears for political and economic stability in Ukraine, a sprawling ex-Soviet republic of 46 million people which borders four EU countries and is the main transit route for Russian gas to Europe.
"We want to send a message that we don't want to live in a police state. We want to live in a modern state and we will achieve this," said Vitaly Klitschko, an opposition leader who says Yanukovich wants to turn the clock back to the Soviet past.
Klitschko, a 2-metre (6 foot 7-inch) tall world heavyweight boxing champion who is increasingly viewed as a national leader-in-waiting, urged all Ukrainians who back a European future for their country to join the rally at 12 p.m. (1000 GMT).
"Our protest is peaceful but we will bring pressure to bear on this government so that our demands are met," he said.
Around 350,000 people joined a similar rally last Sunday, one day after riot police beat protesters and journalists in a crackdown that drew condemnation from Western governments.
Police have since threatened to eject protesters occupying public buildings, including Kiev's City Hall.
"BREAKUP OF COUNTRY"
Speculation has swept Ukraine about whether Yanukovich, who met Russian President Vladimir Putin in the Black Sea resort of Sochi on Friday, may be poised to sign up to a Moscow-led customs union, slamming the door on any move closer to the EU.
Moscow and Kiev both sought to play down the speculation, saying the customs union was not even discussed in Sochi, but they confirmed the two governments would meet on Dec. 17.
"Any signature to a deal on forming a new Soviet Union means the breakup of the country," Arseny Yatsenyuk, a former economy minister now prominent in the opposition, told reporters.
Yanukovich and Putin, who regards Ukraine as strategically vital to Moscow's own interests, are widely believed to have struck a bargain whereby Ukraine obtains cheaper Russian gas and possibly credits in exchange for backing away from the EU.
Ukraine sorely needs external help to meet looming gas bills and debt repayments, but the protesters camped around braziers in Kiev's central Independence Square, braving snow and sub-zero temperatures, say their struggle is about more than money.
"We want our country to be as civilised as the most advanced country in Europe. That means real democracy and equal rights under the law," said Valentina Mysak, 58, who planned to attend Sunday's rally with her daughter and 20 others from her native town of Obukhov, 50 km (30 miles) from Kiev.
"Our hearts demand a revolution," said Dennis Cherniavsky, 25, who works for an agricultural firm.
"This is not any more about joining the European Union, it is about having a humane government." (Writing by Gareth Jones; Editing by Alistair Lyon)