US President Barack Obama has warned that the West would not allow Russia to redraw Europe's borders "at the barrel of a gun", Press TV reported.
At a joint press conference with German Chancellor Angela Merkel at the White House on Monday, Obama said he was considering whether to send lethal arms to Ukraine to help Kiev battle the pro-Russian forces in the country's restive eastern regions.
"The possibility of lethal defense is one of those options that's being examined. But I have not made a decision about that yet," he stated.
"We continue to encourage a diplomatic resolution to this issue," Obama said.
Merkel and many European nations believe sending in weapons would only escalate a conflict that has claimed 5,400 lives in less than a year.
However, Obama is facing increasing calls from domestic critics to send lethal weapons to Kiev.
The US media reported last week that the Obama administration is considering supplying the Ukrainian military with weapons and equipment to fight pro-Russian forces.
The plan has raised many eyebrows among Washington's allies. "The progress that Ukraine needs cannot be achieved by more weapons," Merkel said in Munich on Saturday.
The German chancellor is seeking to negotiate a peace deal with Russian President Vladimir Putin after holding talks in Moscow last week with French President Francois Hollande.
Russia has warned the US against sending weapons to Ukraine, saying the move would cause "colossal damage" to ties between the two countries.
Leaders of Ukraine, Germany, France and Russia are planning to convene in the Belarusian capital city of Minsk later this week, after Merkel leaves Washington.