Russian Foreign Minister Sergei Lavrov said that U.S. plans to send weapons to Ukraine, fighting pro-Russian rebels in its east, would be a direct hit against a Minsk peace agreement struck last month, RIA news agency reported.
Ukraine has requested lethal aid from the United States, where Congress wants a tougher response from President Barack Obama after claims by U.S. intelligence agencies of Russian tanks and artillery crossing into Ukraine.
Moscow denies the claims.
On another note, Ukrainian President Petro Poroshenko urged his country's allies to consider boycotting the 2018 soccer World Cup in Russia if Moscow does not pull all its troops out of his territory, in a German newspaper interview published on Monday.
Poroshenko told Bild he preferred to keep soccer and politics separate but this was not possible when Ukrainian club Shakhtar Donetsk was having to play 1,200 km (750 miles) away in Lviv because Donetsk was occupied by pro-Russian separatists.
"I think there has to be discussion of a boycott of this World Cup. As long as there are Russian troops in Ukraine, I think a World Cup in that country is unthinkable," said Poroshenko, who was in Berlin on an official visit on Monday.
The Ukrainian president said he would ask Germany's Chancellor Angela Merkel to push for tougher sanctions on Russia because of what he described as repeated separatist violations of the ceasefire which she helped broker last month.
He was also going to ask the chancellor for more non-lethal military aid for Ukraine's forces, such as bullet-proof vests.
"We need more to be able to defend ourselves and protect our soldiers. We need radar reconnaissance, drones, radio and night-vision equipment. I am going to talk to the Chancellor about this," said Poroshenko.
"It's not about weapons of attack -- we don't want to attack anyone," he added.
On the field:
One Ukrainian serviceman has been killed in fighting in the separatist-minded east of the country in the past 24 hours despite a ceasefire deal, a spokesman for Ukraine's military said in a televised briefing on Monday.
The death is the first reported loss for the Ukrainian military since March 11. Attacks have fallen significantly in the past two weeks, raising hopes the peace plan, agreed in Minsk in February, could hold.
REUTERS