Washington has said it would welcome "closer cooperation" with Russia over security at the forthcoming Sochi Winter Olympics. Two deadly terror attacks in the regional hub of Volgograd have drawn worldwide condemnation.
The White House said on Monday that it would lend any expertise it could to Russia after two deadly bomb attacks left more than 30 dead.
"The US government has offered our full support to the Russian government in security preparations for the Sochi Olympic Games," White House spokeswoman Caitlin Hayden said. "We would welcome the opportunity for closer cooperation for the safety of the athletes, spectators and other participants."
While Russia is primarily responsible for security at the games, the US Olympic Committee works closely with the US State Department on its security arrangements. The State Department's Bureau of Diplomatic Security typically assists host nations at such events, working in tandem with law enforcement and security officials.
The Russian Health Ministry said on Tuesday the death toll from the attacks has now risen to 34 - 18 from the station bombing and 16 from the trolleybus attack - after three people died of their injuries.
Officials said 65 people have been hospitalized with injuries.
The city is a major regional transport hub, lying about 650 kilometers (400 miles) from Sochi, which is to host the games in February.
Russia's Foreign Ministry on Monday blamed Islamist "bandits" for the attacks, claiming that the bombers had ties to North Caucasus insurgent leader Doku Umarov.
Investigators said the explosives on the trolleybus had been detonated by a male suicide bomber whose body fragments had been taken for genetic analysis. Investigative Committee spokesman Vladimir Markin said the explosives used appeared identical to those in Sunday's train station attack.
"We will continue our fight against the evil enemy with resolve," the ministry said in a statement.
Russian offers assurances
IOC head Thomas Bach condemned the attacks but voiced confidence security would be sufficiently tight at the Olympics. "The Olympic Games are about bringing people from all backgrounds and beliefs together to overcome our differences in a peaceful way," he said.
UN spokesman Martin Nesirky said Russian President Vladimir Putin has assured UN leader Ban Ki-moon "that Russia would work within the bounds of international law to bring the perpetrators to justice."
Ban and the UN Security Council said they were "outraged" by the latest attack.
Meanwhile, the head of the Russian Olympic Committee Alexander Zhukov said the bombings didn't highlight a need for additional security measures, claiming "everything necessary already has been done."
Russia is already preparing to impose a "limited access" security cordon around Sochi from January 7, with all traffic to be checked and cars not belonging to residents to be banned from a wide area around the city.
rc/av (AFP, AP, dpa)