Iranian-backed Shiite militias are threatening to retaliate against American interests inside Iraq if the United States goes ahead with strikes against the Tehran-allied government in Syria, according to Iraqi security officials and militants themselves.

The threats, which come as U.S. President Barack Obama's administration and Congress debate possible military action over the Syrian regime's alleged use of chemical weapons, risk exacerbating an increasingly deteriorating security environment inside Iraq.

The Wall Street Journal reported in its Friday edition that the U.S. has intercepted an order from Gen. Ghasem Soleimani, the head of the Iranian Revolutionary Guard's elite Quds Force, telling Iraqi militias to prepare to strike American interests inside Iraq. The Journal report quoted unnamed American officials, who said the U.S. Embassy was a potential target. The Quds Force oversees external operations of the Guard throughout the world.

Iraq's Shia-led government, which is officially neutral on the Syrian civil war, has bolstered ties with Shia heavyweight Iran in the years since the 2003 U.S.-led invasion, and it is concerned about the threat posed by Sunni extremists, including Iraq's al-Qaeda branch, fighting among the rebels. The government has vowed to prevent such attacks.

In Syria, for the first time in Syria's 2½-year conflict, the government is offering a bounty to anyone who captures foreign "terrorists" —the word authorities use for rebels fighting to topple President Bashar al-Assad.

In a brief statement on Syrian television, authorities said they would give the equivalent of about $4,000 Cdn to anyone who brings in a "non-Syrian terrorist" and about $1,600 to anyone giving information on their whereabouts or if they help apprehend them.

State media said the identities of those who provided information would be kept secret and their "protection ensured".

In an indication that it would grant amnesty to rebels who informed on their comrades, state television added: "Their affairs will be settled if they are Syrians who have been wanted in recent events."

U.S. orders diplomats out of Lebanon

The United States State Department on Friday ordered non-essential U.S. diplomats to leave Lebanon due to security concerns as the Obama administration and Congress debate military strikes on neighbouring Syria.

In a new travel warning for Lebanon, the department said it had instructed nonessential staffers to leave Beirut and urged private American citizens to depart Lebanon.

The step had been under consideration since last week, when President Barack Obama said he was contemplating military action against the Syrian government for its alleged chemical weapons attack last month that the administration said killed more than 1,400 people near Damascus.

"The potential in Lebanon for a spontaneous upsurge in violence remains," the department said.

Russia sends 2nd navy ship toward Syria

Russia, an ally of Assad, is sending the naval landing ship Nikolai Filchenkov to the eastern Mediterranean, state news agency Interfax quoted a navy source as saying on Friday. Russia says its vessels in the eastern Mediterranean guarantee security in the region.

"The vessel will dock in Novorossiysk where it will take special cargo on board and head to the designated area of military service in the eastern Mediterranean," Interfax quoted an unnamed navy source as saying.

It gave no more details and Russia's Defence Ministry declined immediate comment.

Nikolai Filchenkov was not among vessels that the ministry said last month would enter the Mediterranean as part of a planned rotation.

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Russia says it will not get involved militarily in Syria and opposes a possible U.S. intervention, saying it would lack a mandate from the UN Security Council, where Moscow has blocked Western-led attempts to mount pressure on Assad.

The dispute over Syria has overshadowed a G20 summit in St Petersburg, Russia, this week and there is little expectation that world powers will be able to overcome differences on the matter.