Russia has reacted angrily to additional sanctions imposed by the European Union over Moscow's role in the Ukraine crisis, saying they would hamper cooperation on security issues and undermine the fight against terrorism and organised crime.
Russia's Foreign Ministry also said the United States bore shared responsibility for the conflict for pushing Kiev into repressing Ukraine's Russian population.
The EU reached an outline agreement on Friday to impose the first economic sanctions on Russia but scaled back their scope to exclude technology for the crucial gas sector.
After discussions on broadening the sanctions from the current mix of asset freezes and travel bans, the legal instruments required to give effect to the new punitive measures will be taken up on Tuesday, they said.
The European Commission, the EU's executive arm, "will swiftly table the necessary legislative proposals in all areas identified" by member states earlier this week, a statement said.
EU foreign ministers agreed on Tuesday that the Commission and the bloc's external affairs arm should finalise work on tougher measures targeting specific sectors of the Russian economy.
The 28-nation EU toughened its stance towards Russia following last week's downing of a Malaysian airliner, killing 298 people, in an area of eastern Ukraine held by Russian-backed separatists.
In a second statement on Saturday, Russia's Foreign Ministry said Washington shared responsibility for the crisis.
"The United States continues to push Kiev into the forceful repression of (Ukraine's) Russian-speaking population's
discontent. There is one conclusion - the Obama administration has some responsibility both for the internal conflict in
Ukraine and its severe consequences," the ministry said.
In another development, Human Rights Watch (HRW), the New York-based rights monitor, said on Friday that it had found a "mass grave" in the eastern Ukrainian town of Slovyansk.
It also said both warring sides in eastern Ukraine are illegally attacking civilians with unguided rockets.
"Instead of denying it, I think it would be wise for the Ukrainian government to commit to immediately stop using this kind of rockets in populated areas," Ole Solvang, HRW researcher, told Al Jazeera.
For its part, Ukraine blamed the rebels for attacks on civilians, saying "terrorists" are trying to discredit government forces.
Along with the US, Ukraine has also accused Russia of firing across the border into Ukraine and moving in heavy artillery.
Ukrainian President Petro Poroshenko told US Vice President Joe Biden in a telephone conversation on Friday that Ukrainian troops were increasingly coming under direct fire from the Russian side of the border, according to a White House statement.
Andriy Lysenko, a spokesman for Ukraine's National Security and Defence Council, said five salvoes of heavy rockets were fired across the border near the town of Kolesnikov, in the Luhansk region in the country's east.
Russia denied the accusations and charged Ukraine with firing across the border on a Russian village.
It also toughened its economic measures against Ukraine by banning dairy imports.