TEHRAn, YJC.-- US Secretary of State John Kerry said Tuesday he would visit Russia next week for the first time since taking office, with a host of issues including the war in Syria clouding bilateral ties.
His announcement came the day after President Barack Obama stepped up pressure on Moscow over Syria, telling Russian leader Vladimir Putin of his concern about the reported use of chemical weapons by the Damascus regime.
"I will be traveling to Russia next week, and the visit, in my judgment, is overdue," Kerry said after talks with his Spanish counterpart Jose Manuel Garcia-Margallo.
Famously testy relations between Moscow and Washington have grown worse since Putin returned to the Kremlin for a third term last May on the wave of anti-US rhetoric, although on issues such as Iran and North Korea's disputed nuclear programs they have been able to find common ground.
But Washington has been deeply frustrated that Moscow has blocked tougher action against its long-time ally Syria in the UN Security Council, including new sanctions, and has continued to shore up President Bashar al-Assad.
Kerry has already met his Russian counterpart Sergei Lavrov several times since taking up his post as secretary of state on February 1. And it was not immediately clear if he would have talks with Putin.
But the top US diplomat said there was a "range of issues that we need to discuss, from Syria to Iran to the upcoming G-8 summit."
The United States is calling on Assad to allow a United Nations team into the country to assess reports that chemical weapons have been used.
Obama warned Tuesday against a rush to judgment on Syria's use of chemical arms, but said proof of their use would trigger a "rethink" of his reluctance to use military force to aid the opposition in Syria.
Kerry will also want to tap Russian authorities about their probe into the brothers of Chechen origin said to be behind the Boston marathon bombings earlier this month.
Authorities have identified two brothers -- Tamerlan and Dzokhar Tsarnaev -- as the suspects in the bombings in which three people were killed and 260 injured.
Tamerlan Tsarnaev, the elder brother, returned to visit Dagestan in 2012 to obtain a new Russian passport which in the end he never picked up.
The visit is now being closely scrutinized in Russia and the United States to see if the true aim was to activate contacts with Islamists in Dagestan, which has been dogged by an anti-Kremlin insurgency for years.
Kerry will also help prepare a visit by Obama to Moscow later this year which the Kremlin said would take place just before the G20 summit that Russia hosts in Saint Petersburg in early September.
Another issue set to be discussed is Moscow's banning of all adoptions of Russian children by American parents after Washington passed legislation targeting Russian officials suspected of human rights abuses.