U.S. Secretary of State John Kerry on Friday said Russia's President Vladimir Putin won't make decisions on Crimea until after this weekend's referendum, following a "constructive dialogue" with Russian Foreign Minister Sergei Lavrov.
"Our position on the referendum is clear," said Kerry during a press conference. "We believe the referendum is contrary to the constitution of Ukraine."
On Sunday, the people of Crimea go to the polls in a referendum on whether to stay part of Ukraine. Crimea is Ukraine's Black Sea peninsula of nearly two million people and is of extreme strategic importance to Russia because of its geographical location. They are widely forecast to back rejecting Ukrainian rule.
(Read more: Crimea referendum: Why it's so important)
Kerry and Larov also discussed worries over Russian military exercises on Ukraine border and increased anxiety caused within the country.
U.S. stocks wavered around the flatline during Kerry's remarks. Meanwhile, Russia's MICEX index closed down nearly 1 percent Friday. Earlier in the session, the index tumbled more than 5 percent to touch its lowest level in more than four years.
On Thursday, Ukraine's largest bank said jittery customers in the Crimean Peninsula lined up to withdraw cash from their accounts ahead of the referendum.