Secretary of State Condoleezza Rice accused Russia of using its energy wealth as a political weapon, and warned on Thursday that Moscow must play by international rules if it wants to be part of the global economy.

Rice said it was "ironic and not good" that Russia used gas exports to apply pressure to former close ally Ukraine just as Moscow was assuming the rotating presidency of the Group of Eight economic powerhouse nations.

"It was not a good week from the point of view of Russia's demonstrating that it is now prepared to act ... as an energy supplier in a responsible way," Rice told reporters.

"When you say you want to be a part of the international economy and you want to be a responsible actor in the international economy, then you play by its rules," Rice said.

European nations made that point strongly, following moves to drastically raise gas prices or cut off supplies to Ukraine, formerly part of the Soviet Union and until 2004 still largely under Moscow's influence.

The crisis came in the middle of the cold Ukrainian winter and just two months before parliamentary elections in Ukraine. The voting is the first since the tumultuous Orange Revolution mass protests that catapulted to power a critic of Russia, Viktor Yushchenko.

Under international pressure, Russia signed a complicated energy deal with Ukraine this week that keeps gas flowing but requires Ukraine to pay sharply higher prices.

Until Thursday, the United States had expressed concern about Russia's actions but avoided saying Russia had used energy to retaliate against Ukraine for moving toward Western-style democracy.

Ukraine had bought gas from Russia at a steep discount, a relic of the old Soviet system. Rice said there is nothing wrong with ending that arrangement gradually.

"But when you do it in the way that this was done, with an obviously political motive, of course it causes problems," Rice said.

"I think that kind of behavior is going to continue to draw comment about the distance between Russian behavior and something like this and what would be expected of a responsible member of the G-8."

Russia sought G-8 membership for more than a decade partly for the economic clout it carries and partly for the prestige of membership in what had been known as the Group of Seven highly industrialized countries.

The group turned down a U.S. proposal to invite Russia to join as a full member in 1992 — a proposal made as a political gesture to encourage democracy in Russia — but accepted Russia's full-fledged membership a decade later.

Russia assumed the presidency this year and will host the annual G-8 summit this summer in St. Petersburg.

The other members are the world's seven wealthiest nations — United States, Britain, Canada, France, Germany, Japan and Italy.

Russia has the 16th largest economy in the world, but argues that its role as a top energy producer makes it an essential partner.