Iran has received the first installment of $4.2 billion in frozen assets as part of a nuclear deal with world powers, Deputy Foreign Minister Abbas Araqchi told ISNA news agency Saturday.

Unblocking the funds under the landmark deal in which Iran agreed to roll back parts of its nuclear program and halt further advances is expected to breathe new life into its crippled economy.

The United States and EU traded unusually sharp barbs with Russia Saturday over Ukraine's future amid concerns that Kiev could resort to possible military intervention to end anti-government protests.

Neither side pulled any punches, with U.S. Secretary of State John Kerry saying what happens in Ukraine is crucial for Europe's future while his Russian counterpart Sergei Lavrov blasted willful and two-faced Western interference.

Ukraine's opposition warned Saturday the military may move against anti-government demonstrators, ahead of talks with U.S. Secretary of State John Kerry over the country's worst crisis since independence.

The warning came hours after the army weighed in on the crisis for the first time, calling on President Viktor Yanukovych to act urgently to end the turmoil.

While a first round of Syria peace talks in Geneva ended Friday with no concrete results, getting Syria's foes talking is a step in the right direction, a senior U.S. official said.

"It is, I think, significant that throughout the week the two sides agreed to stay in the room ... to talk to each other. That is not a small thing," the U.S. official told reporters on condition of anonymity.

President Vladimir Putin's advisor said on Friday that Ukrainian President Viktor Yanukovych would lose power as a result of the ex-Soviet state's political crisis unless he "quashes the rebellion".

"He (Yanukovych) is currently in the situation of a creeping coup and because he is the guarantor of the Constitution, security and integrity of Ukraine, then the president has no choice," Kremlin economic aide Sergei Glazyev said in remarks released on Friday.

Russia on Friday slammed as a "circus" U.S. Secretary of State John Kerry's planned weekend meeting with Ukrainian opposition leaders.

The top U.S. diplomat is due to meet former boxing champion Vitali Klitschko, leader of the UDAR (Punch) party and opposition leader Arseniy Yatsenyuk on the sidelines of the annual Munich Security Conference on Saturday.

The United States has raised concerns with Moscow over a reported Russian test of a cruise missile and is evaluating whether it breaks a 1987 treaty, a U.S. official said Thursday.

Washington has raised "the possibility of... a violation," State Department spokeswoman Jen Psaki said, amid reports that Russia had tested a new ground-launched cruise missile.

Syrian opposition chief Ahmad Jarba is to visit Moscow on Tuesday at the invitation of Russian authorities, a top aide told Agence France Presse on the sidelines of peace talks in Geneva.

"Mr. Jarba has accepted the Russian invitation and will go to Moscow on February 4," Monzer Aqbiq, head adviser to the leader of the Syrian National Coalition, said on Thursday.

Syria's opposition plans to hold talks with Russia, a long-time ally of their nation's regime, a spokeswoman said Wednesday amid UN-brokered peace talks between the warring sides.

"There is a plan to meet with officials in Moscow, but we have not confirmed the dates," Rafif Jouejati, spokeswoman for the Local Coordination Committees activist network told Agence France Presse in Geneva, where Syrian government and opposition negotiators were into their fifth day of closed-door talks.

Ukraine's parliament on Wednesday launched a debate on whether to grant amnesty for detained protesters as the country's first post-independence president warned of civil war.

A day after scrapping tough anti-protest laws that had ignited the latest political turmoil, deputies met in an extraordinary session to consider granting amnesty to those arrested in the anti-government unrest.