Moscow and Washington have traded fierce diplomatic blows over Syria with US charges that Russia was pushing its ally into civil war and the Kremlin accusing the White House of being emotional.
Thursday's brisk exchanges came as Vladimir Putin, the Russian president, prepared to face a grilling on Friday from the leaders of Germany and France during his first tour abroad since his May 7 inauguration.
Russia has made it clear from the start that Putin will not be swayed by Western and Arab world anger over his refusal to back action against a Middle East government that Moscow has held patronage over since Soviet times.
"Russia's position is well-known. It is balanced and consistent and completely logical," Interfax quoted Putin's spokesman Dmitry Peskov as saying.
"So it is hardly appropriate to talk about this position changing under someone's pressure."
Hillary Clinton, the US secretary of state, used some of her most explicit language to date to indicate that Washington's patience with Moscow was running thin because of its refusal to commit to tougher UN Security Council measures against Syria.
The Russians "are telling me they don't want to see a civil war. I have been telling them their policy is going to help contribute to a civil war," she told a mainly student audience on a visit to Copenhagen.
"We have to bring the Russians on board because the dangers we face are terrible. We know it actually could get much worse than it is."
'Free of emotions'
Russia insists that it is not supporting the government of Syrian President Bashar al-Assad but rather respects international law and the policy of non-intervention in internal conflicts.
That argument has found less currency with foreign powers following the killing last weekend of 108 civilians - almost half of them children - in the Syrian town of Houla that Moscow partially blamed on both sides.
Peskov said Russia's refusal to back further action against Assad after the Houla massacre and other attacks on civilians was based on an approach "completely free of emotions, which are hardly appropriate here".
Al Jazeera's Rory Challands, reporting from Moscow, said: "Russia is scared of losing its influence in Syria.
"But if you look a little bit deeper you can see that maybe Russia's position is softening a little bit. It didn't object to the UN statement condemning the violence … in the weekend.
"And Sergei Lavrov, the foreign minister, said earlier on in the week that the survival of the Assad government was less important than the stopping of all violence in Syria."
Putin is expected to face tough questions from both German Chancellor Angela Merkel and French President Francois Hollande during a three-nation trip starting on Thursday in Belarus - an authoritarian ally he chose as his first foreign destination as head of state.
Hollande has upset Russia by refusing to rule out foreign military intervention, as long as it is carried out with UN backing, to stamp out nearly 15 months of fighting, which observers believe has claimed about 13,000 lives.
However, Ivo Daalder, the US envoy to NATO, said on Thursday that military intervention in Syria is not on the table despite the massacre of civilians.
NATO allies have neither discussed an intervention in Syria nor made any military planning to stop the crackdown, Daalder said.
Battles raged as government troops and rebel forces clashed across Syria on Thursday, the Syrian Observatory for Human Rights (SOHR) said, adding that at least 14 people were killed, including a young boy.
Government forces pounded central Houla for a second consecutive day and used heavy machine gun fire in the town, the Britain-based watchdog said.
Amid the renewed violence, a boy was shot dead by a sniper in Taldu in central Houla, the SOHR said.
"Frightened residents of the area fled" for nearby towns, the organisation said.
In-depth coverage of escalating violence across Syria
In Qusayr, in the central province of Homs, nine people, including a woman and an opposition fighter, were killed by troops shelling and firing heavy machineguns as they tried to capture the opposition bastion, the observatory said.
The SOHR added that government forces suffered heavy losses on Wednesday in Qusayr, though no information was yet available on whether any regulars had been killed in the area.
In Daraya, near Damascus, a woman was shot dead by security forces, the observatory said.
In the northern province of Aleppo, two soldiers were killed by a blast that also injured at least five other members of the security forces, it added.
In Aleppo, a man identified by the observatory as "the brother of a Syrian MP" was shot dead on Thursday, with the organisation quoting anti-government activists as saying "the man's family is very loyal to the government and has participated in the repression of protests".