Kiev, January 28 (RHC)-- The United States has once again threatened to step up sanctions on Russia in an attempt to increase pressure on the Kremlin over the situation in Ukraine. Speaking on a visit to Kiev on Wednesday, U.S. Treasury Secretary Jack Lew said: "We remain prepared to do more (on sanctions) if necessary."

During his visit, Lew signed an agreement with Ukrainian Finance Minister Natalia Yaresko, providing Kiev with $2 billion in loan guarantees to help it with "near-term social spending" in 2015. After signing the loan agreement, the treasury secretary said that "Russian support for separatists in Ukraine" has led Washington and the European Union to impose sanctions on Moscow.

Since last year, the United States and the European Union have set up a network of sanctions on Moscow. The U.S. accuses Russia of arming troops fighting alongside pro-Russian forces in eastern Ukraine, but Moscow denies any involvement in eastern Ukraine.

U.S. President Barack Obama also said on Sunday that the U.S. can help Ukraine's military with "basic equipment." The Pentagon in April 2014 sent hundreds of troops to the Baltic States. The U.S. president also reiterated that Washington and its allies were united against Moscow, a policy he said has left Russia isolated diplomatically and weakened economically.

In response to Obama's remarks about "isolating" Russia, Russian Foreign Minister Sergey Lavrov said that Washington attempts to isolate Russia do not work.