US Secretary of State Condoleezza Rice arrived here Wednesday as the United States and Russia accused each other of stoking violence in Georgia.
Her trip comes a day after she signed a deal allowing Washington to base part of a new US missile defence system in the Czech Republic, prompting a stark warning from Moscow that it would respond militarily.
The former Cold War rivals have traded accusations of fanning separatist tensions in Georgia itself, where violence has flared in the past week in Abkhazia, one of two regions that broke from Tbilisi after the collapse of the Soviet Union.
"Russia has greatly escalated its political and military pressure on Georgia," a senior State Department official told reporters traveling with Rice to Tbilisi, referring to Moscow's moves in the separatist Abkhaz region.
"Russia needs to resume its role as a neutral arbiter of peace rather than a party to the conflict, which Russia is in danger of becoming," the diplomat said on condition of anonymity.
"Russia needs to realise the empire is gone. Russia needs to respect the territorial integrity of its neighbour," he said, adding Rice would reinforce that point during her talks here.
Rice was to have dinner with Georgia's pro-Western president, Mikheil Saakashvili, on Wednesday evening.
The official warned that Washington feared that "a military cycle of escalation will simply develop a momentum of its own and could lead to a catastrophe in the region," one involving "horrific" new "fighting."
Hours before her arrival, Russia's foreign ministry issued a statement accusing Georgia of pushing the region towards war through actions openly supported by the United States.
"Tbilisi's actions represent a real threat to peace and security in the South Caucasus, capable of taking the region to the brink of a new armed conflict," the ministry said in a statement.
The ministry said those who "shield the provocateurs and blame everything on Moscow are doing a great disservice to the Georgian leadership and strengthening its sense of impunity."
The statement explicitly referred to the US State Department.
Russia's sharp words came after Rice, as she prepared to sign the missile defence agreement in Prague, publicly blamed Russia for instability in Georgia.
After meeting US President George W. Bush at the Group of Eight summit in Japan, Russian President Dmitry Medvedev said the signing of the missile defence agreement in Prague had left Russia "most distressed."
"Russia isn't going to get hysterical but will be studying countermeasures," Medvedev said, in a reminder of previous Russian threats to target European neighbours in response to the US missile shield.
Russia's foreign ministry made a more specific threat on Tuesday, saying that if the US missile shield was deployed near Russia's borders, "we will be forced to react... with military resources."
Russia has long argued that it regards the US missile system, which so far calls for a powerful radar tracking station in the Czech Republic and 10 interceptor missiles possibly in Poland, as a threat to its own security.
Washington insists it is solely aimed at shielding the United States and its allies from missile attacks from "rogue" states such as Iran.
Meanwhile, Georgia's Saakashvili says he wants his country to become a member of the US-led NATO military alliance, a move viscerally opposed by Russia and strongly backed by the United States.
The Russian foreign ministry on Wednesday said it thought Georgia may have been involved in at least some of a string of bombings in Abkhazia last week that killed four people and injured 16 others. Georgia has denied involvement.
Russian peacekeepers have also accused Georgia's military of making the latest in a string of fighter jet flights over separatist South Ossetia in violation of a ceasefire. Georgia denied this, saying that four Russian jets had illegally overflown the area.
Abkhazia and South Ossetia gained de facto independence from Tbilisi after fighting brief wars against Georgian forces following the Soviet Union's 1991 collapse.
Tbilisi says the regions are an integral part of Georgia, but has offered Abkhazia autonomy within Georgia.
