KIEV, June 28 - Viktor Yanukovych, the leader of the largest opposition group in Parliament, sharply criticized the government??™s plans to re-negotiate a key natural gas agreement that been signed between Ukraine and Russia in January.

Yanukovych said the revision of the deal would trigger massive street protests throughout Ukraine and would undermine relations with Russia, Ukraine??™s biggest neighbor and a major source of natural gas.

???This is an attempt to instigate anti-Russian mood in Ukraine and is an attempt by the government to cover up its incompetence,??? Yanukovych said in an interview with Izvestia, a Russian daily, published Wednesday. ???If the government moves to revise the agreement without any reason, tomorrow the entire Ukraine would rise against this [government].???

The comment shows a dramatic turnaround in position of Yanukovych??™s party, which controls 186 seats in 450-seat Parliament. The party had been denouncing the agreement ever since it was signed in January to end a major gas price dispute between Ukraine and Russia.

The development underscores rising tensions between the pro-Western coalition, which has last week pledged to form the new government in Ukraine, and pro-Russian opposition groups, such as Yanukovych-led Regions Party.

The sudden support for the agreement comes as the Regions Party has been increasingly challenging the coalition in other areas, such as successfully carrying out its threat to block Parliamentary sessions.

A group of opposition lawmakers shut electronic voting equipment in Parliament on Tuesday while others swarmed around a tribune effectively blocking the session and forcing coalition lawmakers hold an urgent meeting in other room.

Gazprom and Naftogaz Ukrayiny, the national oil and gas company, signed the agreement on Jan. 4 after an escalating dispute had led to brief disruptions in Russian natural gas supplies to Europe.

In the agreement, Naftogaz agreed to a 90% hike in Russian gas prices to $95 per 1,000 cubic meters, while Gazprom agreed to a 40% hike in transit costs to $1.6 for shipping 1,000 cu m for a distance of 100 km.

Gazprom has originally insisted on increasing the price to $230/1,000 cu m, which is why the Ukrainian government had been defending the agreement as a victory for Ukraine.

Most of other countries in the region, such as Moldova and Georgia, pay $120/1,000 cu m of Russian gas.

The agreement also made RosUkrEnergo, a Swiss-registered natural gas trader thought to be controlled by Gazprom, as Ukraine??™s only supplier of natural gas for the next five years.

Media reports suggested that RosUkrEnergo may be secretly owned by people representing powerful Russian political figures and possibly even organized crime leaders. RosUkrEnergo denied the reports.

Yulia Tymoshenko, prime minister designate, said last week that she will seek to renegotiate the agreement to replace RosUkrEnergo from the gas shipment business between Ukraine and Russia.

Tymoshenko??™s plans triggered an immediate reaction from Gazprom and from Russian political commentators.

The plans are ???an alarming bell for Europe,??? Sergei Kupriyanov, a spokesman for Gazprom, said. ???It may lead to a crisis.???

Sergei Markov, a Kremlin-linked political commentator, said the revision of the gas agreement would lead to ???a full scale gas war??? between Ukraine and Russia that ???will affect much of Europe.??? (tl/ez)