Russian President Vladimir Putin has made a direct personal appeal to the American people over the Syrian crisis.
In an opinion article in the New York Times, he warns that a US military strike against Syria could unleash a new wave of terrorism.
He says millions of people see the US not as a model of democracy but as relying on brute force.
Later on Thursday, the US and Russia are due to hold talks in Geneva on Syria's chemical weapons arsenal.
Moscow, an ally of embattled Syrian President Bashar al-Assad, has proposed putting the weapons under international control.
The proposal - which Damascus has agreed to - led US President Barack Obama to put military action against Syria on hold in favour of diplomacy.
The US blames the Syrian government for a chemical weapons attack near Damascus last month that killed hundreds. Syria blames the attack on rebels.
As the diplomatic efforts continue, the Syrian army has been trying to retake the Christian town of Maaloula which was overrun by rebel forces - including members of the al-Qaeda-linked al-Nusra Front - at the weekend.
The BBC's Jeremy Bowen, who is in Maaloula, says fighting has been continuing despite earlier reports that government forces had retaken the town.
In the New York Times article, Mr Putin says recent events "have prompted me to speak directly to the American people and their political leaders".
He warned that the UN could suffer the same fate as its precursor, the League of Nations, if "influential countries bypass the United Nations and take military action without Security Council authorisation".
"The potential strike by the United States against Syria, despite strong opposition from many countries and major political and religious leaders, including the Pope, will result in more innocent victims and escalation, potentially spreading the conflict far beyond Syria's borders," he says.
"A strike would increase violence and unleash a new wave of terrorism. It could undermine multilateral efforts to resolve the Iranian nuclear problem and the Israeli-Palestinian conflict and further destabilise the Middle East and North Africa. It could throw the entire system of international law and order out of balance."
Mr Putin said Russia was not protecting the Syrian government "but international law".
He reiterated Russia's opinion that the gas attack of 21 August was probably carried out by opposition forces "to provoke intervention by their powerful foreign patrons".
"Reports that militants are preparing another attack - this time against Israel - cannot be ignored," he adds.
"It is alarming that military intervention in internal conflicts in foreign countries has become commonplace for the United States. Is it in America's long-term interest? I doubt it. Millions around the world increasingly see America not as a model of democracy but as relying solely on brute force."
The article comes as US Secretary of State John Kerry prepares to meet his Russian counterpart Sergei Lavrov in Geneva to discuss Moscow's proposal. It is not clear how long the talks will last.
On Wednesday, envoys of the five permanent UN Security Council members met in New York to discuss the plan.
A UN diplomat quoted by AFP news agency said those present at the 45-minute meeting set out their positions "but there were no real negotiations".
One diplomat told the BBC that the UN envoys' talks were largely symbolic and that the serious questions would be left for Geneva.
Republican Senator John McCain, who has long argued for US intervention in Syria, said he was sceptical about Thursday's meeting.
"Frankly I'm puzzled why John Kerry has to go to Geneva to negotiate with Lavrov," he said.
"Why doesn't Lavrov come to the UN and everybody agree on a resolution and pass it? It's got to be a resolution through the Security Council."
Diplomats predict that talks at the UN Security Council will continue for several days after the Geneva meeting before any resolution can be put to a vote.
France has already been working on a draft resolution that would be enforced by Chapter VII of the UN charter, which would in effect sanction the use of force if Syria failed in its obligations.
However, Russia has already indicated that this would be unacceptable, as would any resolution blaming the Syrian government for chemical attacks.
The 15-member UN Security Council has been deadlocked for months over Syria.
It is facing mounting criticism over what UN Secretary General Ban Ki-moon has called its "embarrassing paralysis" over the conflict.
More than 100,000 people have died since the uprising against President Assad began in 2011.
Russia, supported by China, has vetoed three resolutions condemning the Assad government and threatening it with sanctions.
On Wednesday, the US state department confirmed that Mr Kerry would also meet UN-Arab League special envoy on Syria Lakhdar Brahimi in Geneva.
A team of US arms experts is accompanying Mr Kerry.