US Secretary of State John Kerry on Tuesday defended Russia's efforts against those who doubted the country would play a positive roll in ending hostilities in the Middle East.
"If they hadn't played a constructive role, we would not have had an agreement with Iran," he told the Charlie Rose show.
"If they hadn't played a constructive role, we would not have gotten the chemical weapons out of Syria [...] we would not have gotten the cessation of hostilities or everybody at the table in Geneva," Kerry added.
Ahead of a new round of negotiations in Geneva
, Kerry reiterated his belief that Syrian President Bashar Assad would ultimately need to step down in order for peace to be achieved.
"You can't end the war, because the opposition will not [...] end fighting because of what he is deemed to have done to their people, to the people of his country," Kerry said.
Assad has said he thinks the Geneva talks can produce a new Syrian government that includes opposition, independents and loyalists, but has rejected the idea of a transition authority.
But Syria's opposition has consistently said it wants a halt in attacks on civilians and for the Geneva talks to result in a transitional governing body for Syria that does not include Assad.
During the interview, Kerry was also asked about US Republican presidential front-runner Donald Trump's recent foreign policy proposals.
The New York billionaire said Japan and South Korea, two US allies, should build nuclear weapons to deter enemies.
"I can't think of anything that would be more volatile, more contrary to peace and stability in the region, more contrary to the fundamental commitment of every president since World War II to try to minimize the risk of nuclear weapons and minimize the number of people who have them," Kerry said.