MOSCOW: Russian troops in the breakaway province of South Ossetia have been put on increased combat readiness amid rising tensions on the de facto border with Georgia, according to officials.

Andrei Nesterenko, the spokesman for Russia's Foreign Ministry, said Tuesday the move was a response to Georgian "provocations" and meant to prevent more violence.

"The most important thing now is to prevent escalation and not to allow skirmishes to grow into bigger clashes," Nesterenko said.

The situation near South Ossetia has become increasingly tense as the first anniversary of the Russian-Georgian war approaches Friday, with Georgia and Russia blaming each other for provocations and intentions to resume fighting.

Russian President Dmitry Medvedev called U.S. President Barack Obama late Tuesday "to wish him happy birthday," and during the conversation the two leaders "discussed the situation in Georgia and the need to decrease tensions in the region," the White House said in a statement.

Obama "reiterated the importance of working through established crisis management mechanisms such as the Joint Incident Prevention and Response Mechanism and underscored the need for international monitors," the statement said.

The Kremlin said in a statement that Obama and Medvedev discussed the "lessons of last year's Georgian crisis." There was no elaboration.

Obama said during a recent summit in Moscow that Georgia's territorial integrity must be respected.

The August 2008 conflict erupted after escalating exchanges of fire between Georgia and Moscow-backed South Ossetian forces.

South Ossetia's separatists and Georgian authorities have accused each other of firing guns and mortar rounds on several occasions over the past few days.

The separatist leader, Eduard Kokoity, told The Associated Press in an interview Tuesday that "there is a danger that August 2008 will be repeated."

"Today, Georgia's military is more combat-ready and has a stronger potential" than during the run-up to last year's conflict, Kokoity said.

In the latest incident, Monday night, South Ossetia's separatist authorities said three mortar rounds were fired into South Ossetia from Georgian-controlled territory. Georgian authorities denied the claim and accused separatists of firing rocket-propelled grenades at a Georgian checkpoint near South Ossetia. No one was hurt.

The European Union said it was concerned about mutual accusations of shelling and other incidents, but added that EU monitors in Georgia had seen no evidence confirming them so far.

"The EU urges all sides to refrain from any statement or action that may lead to increased tensions at this particularly sensitive time," the international organization said in a statement late Monday.

EU monitors are the only international ones remaining in Georgia, but they are blocked from traveling inside South Ossetia and Abkhazia, another breakaway region in Georgia.

An EU-brokered truce ended the five-day August war between Georgia and Russia. Russia sent in thousands of troops and tanks that routed the Georgian military and drove deep into Georgia.

Georgian authorities claimed they had to launch the artillery barrage on Tskhinvali, the provincial capital, because Russian troops had moved into South Ossetia hours earlier. Russian officials denied this, and claimed the country acted to protect its peacekeepers and civilians there.

After the war, Russia recognized South Ossetia and Abkhazia as independent nations and permanently deployed thousands of troops there.

The only other country to recognize the regions' independence is Nicaragua.

Georgian President Mikhail Saakashvili said in an interview with France's RTL radio broadcast Tuesday that there is a risk of a new conflict because Russia was putting constant pressure on Georgia. He said Georgia would not engage in conflict with Russia but would defend itself if necessary.

Meanwhile, a senior Russian diplomat voiced concern about what he said were U.S. plans to provide military assistance to Georgia.

"Washington is playing the key role in rearming the Georgian military machine," Grigory Karasin, a deputy foreign minister, said in comments reported Tuesday by the Interfax agency. "It would be in the interests of Georgian democracy ... to refuse to arm this country at all."

South Ossetia's Kokoity echoed Karasin's sentiments, saying countries that arm Georgia "are responsible for any further (military) developments."

On Tuesday, U.S. officials said that they have not ruled out providing defensive weapon systems for Georgia despite warnings by Russia.

Assistant Secretary of Defense Alexander Vershbow told lawmakers at a Senate hearing that U.S. military aid to Georgia was focused on training and modernization of Georgia's military.

But he added that "other forms of assistance can take place. Nothing is off the table."

Assistant Secretary of State Philip Gordon said at the same hearing that there "is no arms embargo on Georgia."

The U.S. is discussing a Georgian request for $16 million in military aid this year, with most of the money intended for training and technical assistance. But Washington reacted coolly after Saakashvili told The Washington Post that Georgia was interested in acquiring heavy weapons for defensive purposes.