A senior U.S. diplomat visiting Russia will press Moscow on a reported deal to sell Syria fighter jets, something Washington described as "quite concerning," the State Department said.

Jeffrey Feltman, the top U.S. diplomat for the Middle East, was in Moscow on Monday and Syria was "issue number one on his agenda," U.S. State Department spokeswoman Victoria Nuland told reporters in Washington.

Syria has signed a $550 million (425 million euro) contract to purchase 36 Yak-130 advanced training fighter planes from Russia, the Kommersant business daily reported on Monday.

The deal was signed in December with Russia's Rosoboronexport state defense corporation, Kommersant cited a source close to the agency as saying, adding that production of the jets would begin once the advance payment was made.

Arab foreign ministers meeting in Cairo on Sunday decided to go to the U.N. Security Council to seek its support for the Arab League’s decisions aimed at resolving the Syrian crisis.

The Arab League "has decided to go to the U.N. Security Council to seek its support for the Arab initiative and we're not seeking internationalization or a military solution," Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani, the head of an Arab taskforce on Syria, clarified after the meeting.

The opposition Syrian National Council plans to send a delegation to the United Nations to press the U.N. Security Council for intervention in unrest-swept Syria, an SNC spokesman told Agence France Presse on Sunday.

"The Council will send a delegation to the United Nations to submit a letter calling for the referral of the Syria file to the Security Council to protect civilians," Mohammed Sermini said in Cairo.

Opposition Syrian National Council leaders on Saturday pressed the Arab League to turn the Syria crisis over to the U.N., but the League looked set to extend its own mission criticized for its failure to stem 10 months of killing.

SNC chief Burhan Ghaliun met Arab League head Nabil al-Arabi in Cairo and lobbied against the extension of the League's peace mission, SNC spokeswoman Basma Qadmani said.

Syrian security forces on Friday killed 13 people across the country, activists said, as pressure mounted on the Arab League to seek U.N. intervention in the face of growing frustration that the bloc's hard-won observer mission in Syria has failed to staunch 10 months of killing.

Meanwhile, thousands of people poured out of mosques after Friday prayers to call for the ouster of President Bashar al-Assad's regime, after choosing "Prisoners of the Revolution" as the slogan for this week's main protests.

Interior Minister Marwan Charbel denied on Thursday that the investigators of the U.N.-backed court probing the assassination of former Prime Minister Rafik Hariri requested the fingerprint records of some Lebanese citizens.

“What some media reported that the Special Tribunal for Lebanon investigators requested the fingerprints of some Lebanese, is not true,” Charbel told al-Manar television.

Foreign Minister Sergei Lavrov on Wednesday defended Russia's trade with Syria amid growing controversy over a mysterious shipment that reportedly delivered a supply of arms to Damascus.

Lavrov was asked to address criticism from Washington's U.N. Ambassador Susan Rice that followed reports that the shipment brought munitions to President Bashar Assad's forces amid their crackdown on protesters.

Russia warned Wednesday that a military strike on Iran would be a "catastrophe" with the severest consequences which risked inflaming existing tensions between Sunni and Shiite Muslims.

"As for the chances of this catastrophe happening, you would have to ask those constantly mentioning it as an option that remains on the table," Foreign Minister Sergei Lavrov said when asked on the chances of military action.

Russia on Wednesday accused Western powers of trying to "suffocate" the Iranian economy and incite popular discontent with new sanctions such as a proposed oil embargo.

Foreign Minister Sergei Lavrov said all sanctions aimed at winning more transparency from Iran concerning its nuclear program had "exhausted" themselves and new measures threatened to only hurt the Iranian people.