Top diplomats have agreed to take immediate steps toward calming tensions in Ukraine, Russia's foreign minister says.
Sergey Lavrov says the four parties gathered in Geneva - the US, European Union, Ukraine and Russia - will work to establish a broad national dialogue to ensure that people's rights are protected.
He said that amnesty will be given to pro-Russian protesters who participated in an uprising against the government in Kiev, except those found guilty of capital crimes.
The tentative agreement could put on hold - for now at least - economic sanctions the West had prepared to impose on Russia if the talks were fruitless. And that would ease international pressure both on Moscow and nervous European Union nations that depend on Russia for their energy.
The announcement came after t hree pro-Russian militants died and 13 were wounded when Ukrainian troops repelled an attack on a National Guard base in the Black Sea port of Mariupol.
A crowd of around 300 men armed with stun grenades and Molotov cocktails attacked the base, in the south-east part of the country, the interior ministry said. Servicemen inside fired warning shots but the attackers did not stop the assault and the army responded.
There were no casualties among the Ukrainian servicemen, the ministry said, and 63 attackers were detained.
The agreement, reached after seven hours of negotiation, requires all sides to refrain from violence, intimidation or provocative actions. It calls for the disarming of all illegally armed groups and for control of buildings seized by pro-Russian separatists during the protests to be turned back over to authorities.
It also gives amnesty to protesters who comply with the demands, except those found guilty of committing capital crimes.
Monitors with the Organisation of Security and Cooperation in Europe will be tasked with helping Ukraine authorities and local communities comply with the requirements outlined in the agreement. And Kiev's plans to reform its constitution and transfer more power from the central government to regional authorities must be inclusive, transparent and accountable - including through the creation of a broad national dialogue.
Russian President Vladimir Putin criticised the US and its European allies for having what he called a double standard and said he hoped he would not have to deploy troops to Ukraine.
Ukraine was hoping to use the Geneva talks - the first of their kind over the crisis that threatens the new government in Kiev - to placate Russia and calm hostilities with its neighbour even as the US prepared a new round of sanctions to punish Moscow for what it regards as fomenting unrest.
Meanwhile, Russia was honing a strategy of its own: Push the West as far as possible without provoking crippling sanctions against its financial and energy sectors or a military confrontation with Nato.
In a television appearance in Moscow today, Mr Putin denied claims that Russian special forces were fomenting unrest in eastern Ukraine. He called the Ukrainian government's effort to quash the uprising a "crime".
In Washington, Defence Secretary Chuck Hagel said the US would send non-lethal assistance to Ukraine's military in light of what he called Russia's ongoing destabilising actions there. He told a Pentagon news conference that the military assistance to Ukraine will include medical supplies, helmets, water purification units and power generators.
Ukraine has asked for military assistance from the US, a request that was believed to include lethal aid like weapons and ammunition. Obama administration officials have said they were not actively considering lethal assistance for fear it could escalate an already tense situation.
The US has already sent Ukraine other assistance, such as pre-packaged meals for its military.
In Brussels, Nato chief Anders Fogh Rasmussen said the military alliance would increase its presence in Eastern Europe, including flying more sorties over the Baltic region west of Ukraine and deploying allied warships to the Baltic Sea and the eastern Mediterranean. Nato's supreme commander in Europe, US Air Force Gen. Philip Breedlove, told reporters that ground forces also could be involved at some point, but gave no details.
Officials said a full-scale Russian invasion of eastern Ukraine would result in broad US and European sanctions on key Russian economic sectors, including its powerful energy industry.