Russian President Vladimir Putin said there is a "real chance" to resolve the decade-long standoff over Iran's nuclear program.
The Kremlin said Monday that Putin delivered the statement in a telephone conversation with Iranian President Hassan Rouhani, who welcomed Russia's efforts in the negotiations.
Russia is one of six nations, including the United States, set to take part in another round of talks with Iran on Wednesday in Geneva, as they seek to address concerns that Iran is pursuing nuclear weapons.
Following the phone call, Iran's president tweeted that during the previous round of talks in Geneva the sides were quite close to an agreement but warned "resorting to excesses could complicate our journey to a win-win outcome."
Rouhani also tweeted that all of Iran's nuclear activities "are peaceful" and under the supervision of the United Nations' nuclear agency [International Atomic Energy Agency].
U.S. President Barack Obama is set to meet Tuesday with key U.S. lawmakers at the White House. Aides say the president will update them on the upcoming negotiations with Iran.
Some lawmakers have called for imposing new sanctions on Iran, saying such measures will help force Tehran to give up its nuclear program. Obama has asked for a pause in any new sanctions, saying diplomacy should be given more time to work.
The six world powers that also include Britain, France, China and Germany want Iran to curb its enrichment activity, while Iran is seeking relief from sanctions that have hurt its economy.
Separately Monday, Iran unveiled its newest drone aircraft. Officials say the 'Fortros' has a range of 2,000 kilometers and can stay airborne for up to 30 hours.
Iran's defense minister said the drone would be used for reconnaissance and patrolling missions.