A top US diplomat has said the United States will supply lethal arms to Ukraine if “aggression” from pro-Russian forces persists, but warned that Moscow would easily match the effort by sending more weapons into the country.

Deputy Secretary of State Antony Blinken said Friday that the US was already moving to provide the Ukrainian military with non-lethal military assistance.

"But if the aggression continues, I think there will be more and more pressure to give them other means to protect themselves," Blinken said in the interview with German radio (DLF), according to Reuters.

"And you know, it's certainly true that, were any of us to provide weapons to Ukraine, Russia could match that and then double that and triple that and quadruple that," he stated.

Some US and European officials are worried that providing lethal weapons to Ukraine would escalate a conflict that has killed about 6,000 people since last April, and drag them into a proxy war with Russia.

However, some members of Congress have stepped up pressure on the White House to counter what they see as increased aggression by Moscow.

“We urge you to quickly approve additional efforts to support Ukraine's efforts to defend its sovereign territory, including through the transfer of lethal, defensive weapons systems to the Ukrainian military," read a letter Thursday to President Barack Obama by 11 lawmakers.

House Speaker John Boehner, House Majority Leader Kevin McCarthy, and top Republicans and Democrats on various House committees signed the letter.

Obama’s lack of “overall strategy thus far has done little to reassure our friends and allies in the region," they wrote in the letter.

Last month, Obama said his administration was still considering sending lethal aid to Ukraine, saying, "If, in fact, diplomacy fails, what I've asked my team to do is to look at all options."

The top US military general has also called on the Obama administration to consider providing lethal arms to Ukraine.

“I think we should absolutely consider lethal aid and it ought to be in the context of NATO allies because Putin’s ultimate objective is to fracture NATO,” Chairman of the Joint Chiefs of Staff General Martin Dempsey told the Senate Armed Services Committee Tuesday alongside Ashton Carter, the new Pentagon chief.

The general’s remarks echo similar pleas made in recent months by several top American officials, including Director of National Intelligence James Clapper.

Washington accuses Moscow of arming and supporting pro-Russian forces fighting in eastern Ukraine. The Kremlin, however, calls the accusation "groundless."

HRJ/HRJ