Presidents Barack Obama and Vladimir Putin confronted one another in telephone talks Monday as a standoff over Ukraine escalated after the CIA chief visited Kiev and a Russian war plane "buzzed" a U.S. destroyer.
Washington said it was consulting European allies and hinted that more sanctions on Russia's economy could be coming, to punish what it sees as Moscow's sponsorship of pro-Russia violence in eastern Ukraine.
The Kremlin said that Putin used the latest in a string of tense phone calls with Obama to brand U.S. charges of meddling in eastern Ukraine as "unfounded."
There were no immediate readouts of the call from the White House, which earlier was the first to say it would take place.
Unusually though, the White House did offer some details of CIA chief John Brennan's travel, confirming Russian media reports that the top U.S. spy had flown into Kiev over the weekend.
Russian Foreign Minister Sergei Lavrov had demanded an explanation over Brennan's visit.
Russia's Interfax news agency quoted an unidentified source as saying Brennan recommended Kiev use force against pro-Russian militants in eastern districts.
But Carney blasted claims that Brennan's travel was anything but routine -- and said he was revealing Brennan's travel to rebut "false claims" laid by Russia.
"Senior-level visits of intelligence officials are a standard means of fostering mutually beneficial security cooperation, including US-Russian intelligence collaboration going back to the beginnings of the post-Cold War era," he said.
"To imply that U.S. officials meeting with their counterparts (in Kiev) is anything other than in the same spirit is absurd."
- 'Provocative' -
Carney also denied that a new Cold War was brewing between Russia and the United States, but an incident involving a Russian jet over the Black Sea and a U.S. cruise missile destroyer did hark back to the tensions of that earlier era.
The Pentagon said the Su-24 fighter made several low-altitude, high-speed passes near the USS Donald Cook, cruising in international waters off Romania over the weekend.
"The aircraft did not respond to multiple queries and warnings from Donald Cook," said Colonel Steven Warren, a Pentagon spokesman.
"This provocative and unprofessional Russian action is inconsistent with international protocols and previous agreements on a professional interaction between our militaries."
The vessel was sent to the Black Sea in a show of Washington's solidarity with its Eastern European NATO allies concerned about Russia's incursion into Crimea.
The plane was about 1,000 meters (3,300 feet) from the American ship but did not directly traverse its decks, a military official told AFP on condition of anonymity.
The White House and the State Department signaled fresh sanctions could be coming for Russia over what Washington says are provocations in eastern Ukraine, including the seizure of administrative and police buildings by Moscow-backed armed groups.
"We feel very strongly that the pattern of activities bear striking similarities to the situation in Crimea ahead of the illegal Russian occupation and purported annexation of that part of Ukraine," said State Department spokeswoman Jen Psaki.
"All evidence points to the likelihood that these are individuals with strong ties to the Russian government who are causing these conflicts in eastern Ukraine."
In a new sign of US pressure on European allies, Obama spoke to French President Francois Hollande by telephone.
Hollande spoke of France's "determination to put in place, with its European partners, a policy of firm, progressive sanctions," his office said.
In a call with German Chancellor Angela Merkel on Friday, Obama had warned that the EU and the United States should be prepared to meet further Russian escalations with tougher sanctions.
Washington and the EU have already imposed sanctions on key individuals in Crimea and officials around Putin and several Kremlin-linked firms.
Western nations have warned they could go after the Russian economy, including in the mining, finance and energy sectors, if Moscow does not change course.
But since such a move could also harm fragile European economies, they remain a political heavy lift for many of the continent's leaders.
The EU agreed to extend a list of asset freezes and visa bans on top Russian officials, but held off on tougher measures until after a meeting of key officials from the EU, United States, Ukraine and Russia in Geneva on Thursday.
Psaki defended the meeting, amid complaints in Washington that it was irrelevant to fast-escalating events.
"We feel there should always be an opportunity and an opening for diplomacy," she said.
As part of its steps to support Ukraine's tottering economy, Washington also formally signed a $1 billion loan guarantee for Kiev, passed by Congress earlier this month.
Treasury Secretary Jack Lew signed the deal with Ukrainian Finance Minister Oleksandr Shlapak in Washington.
[Image via Agence France-Presse]