The Kremlin entered a new battlefield with the West over the weekend, with Washington and London accusing President Dmitry Medvedev of reneging on a promise with Russia's decision to block United Nations sanctions against Zimbabwe.

Moscow and Beijing both used their veto power Friday in the UN Security Council to derail an arms embargo and financial and travel restrictions on President Robert Mugabe, recently sworn in for a new term after conducting what his country's opposition called a campaign of intimidation that killed dozens of people.

While Zimbabwe welcomed the veto as just, Washington and London attacked Moscow's credibility as a G8 partner.

In an unusually harsh statement, Zalmay Khalilzad, the U.S. ambassador to the United Nations, accused Medvedev of going back on an earlier promise and "standing with Mugabe against the people of Zimbabwe."

"The U-turn in the Russian position is particularly surprising and disturbing ... [and] raises questions about its reliability as a G8 partner," Khalilzad said in a statement published on his mission's web site.

He said Medvedev had supported a G8 decision on Tuesday "to take further steps inter alia introducing financial and other measures" against those responsible for the violence in Zimbabwe only a few days earlier.

British Foreign Secretary David Miliband said he was "very disappointed" about the veto.

"It will appear incomprehensible to the people of Zimbabwe that Russia, which committed itself at the G8 only a few days ago to take further steps, including introducing financial and other sanctions, should today stand in the way of timely and decisive Security Council action," he said in a statement.

In Moscow, the Foreign Ministry retorted Saturday that it was "impermissible" to doubt Russia's worthiness as a G8 partner.

"The American and British UN representatives in the best-case scenario are totally uninformed about the discussion of the G8 leaders in Toyako, and in the worst case they are deliberately distorting the facts," it said in a terse statement.

During the G8 summit in the Japanese resort town of Toyako, Medvedev voiced considerable hesitancy about U.S. and British calls to impose sanctions on Zimbabwe. After much deliberation, he joined in a summit declaration Tuesday that called for "financial and other measures" against the Zimbabwean officials responsible for violence, but he said the measures would not necessarily be sanctions.

A Kremlin spokesman declined immediate comment Sunday and pointed to the Foreign Ministry's statement.

Russia's stance appeared to reflect an unwillingness to go after governments for elections criticized by the West. Medvedev's own election in March has faced criticism.

At the UN Security Council, however, Russia adopted the stance that Zimbabwe's situation was an internal affair and outside the mandate of the UN. Russia's G8 envoy, Alexander Pankin, had warned at the G8 summit that meddling in Zimbabwe's internal affairs might trigger an unpredictable outcome.

Britain's UN ambassador suggested that Russia had worked to bring the Chinese along on the veto. Beijing would not have used its veto if Russia had supported the resolution because it does not want to court international controversy ahead of next month's Olympic Games, the ambassador, John Sawers, told Britain's The Daily Telegraph newspaper.

China has become a huge investor in Africa in recent years, pouring billions of dollars into its fast-growing economy.

But analysts said Moscow's veto seemed to be motivated by political rather than business interests. "The Russians do not want to part company with members of the non-Western world," said Dmitry Trenin from the Carnegie Moscow Center. "The Russians see themselves as a leader of the opposition inside the UN."

Roland Nash, head of research at Renaissance Capital, said that while Russia has some business interests in Africa, policy overrode any business angle in the Security Council vote. "While there are a lot of opportunities in the region, there is not much business taking place in Zimbabwe because of the politics there," he said.

Yet Russian businesses have been quietly exploring opportunities in the country, casting aside concerns about an official inflation rate that has surpassed 300,000 percent as the country endures its 10th year of recession.

Billionaire Roman Abramovich visited the country in March. Zimbabwe's state media reported at the time that he was interested in the Hwange Colliery coal mine, which he visited. Tourism officials seized upon the visit as a sign that the country was safe for tourists and open for business. Abramovich's spokesman insisted that the trip was a private one, made for tourism only.

Renaissance Capital has sent teams of specialists to Zimbabwe over the past year to explore investment opportunities.

The bank started an Africa fund last year and has set up offices in Nairobi, Kenya, and Lagos, Nigeria, all the while keeping quiet about the fact that it has its eyes trained on Zimbabwe. "The [investment situation] is so mispriced," said a source inside the bank. "It's an educated society. You can trust people, despite the fact that there is runaway inflation, the judicial system doesn't function, and [there is] no democracy."

Human rights activists also expressed dismay at Russia's veto.

"The actions of Russia show yet again how certain members of the international community continue to let down the people of Zimbabwe who courageously voted for change in the elections," Georgette Gagnon, Africa director at Human Rights Watch, said Sunday by telephone from New York.