By Alexei Anishchuk
MOSCOW (Reuters) - A senior lawmaker and ally of President Vladimir Putin suggested on Wednesday that Russia could increase arms sales to Iran or review cooperation over Afghanistan if the United States launches military strikes against Syria.
Russia is a long-standing ally of Iran, Syria's main backer and the United States' chief antagonist in the Middle East. Moscow built Iran's first nuclear power station and has supplied it with anti-aircraft defenses.
The remarks by Alexei Pushkov, head of the lower house of parliament's foreign affairs committee, appeared to be part of a drive to convince Washington to refrain from attacking Syria in retaliation for a poison gas attack in Damascus that killed hundreds of civilians.
Pushkov echoed Putin by saying Russia's initiative to have its ally Syria give up all its chemical weapons would succeed only if Washington and its allies rejected the use of force.
Outlining possible responses if Syria was attacked, Pushkov told the lower house, the State Duma: "This would include the expansion of defensive weapons deliveries to Iran, and discussing the possibility of reviewing our cooperation with the United States on Afghanistan."
He gave no details in his address to the chamber, which was expected to pass a resolution later on Wednesday echoing Putin's opposition to military strikes.
The Russian business daily Kommersant said Putin and Iranian President Hassan Rouhani could agree a deal on supplying Tehran with Antey-2500 anti-aircraft missiles when they meet on the sidelines of a regional summit in Kyrgyzstan on Friday.
But Interfax news agency later quoted a military source as playing down expectations of such an agreement.
Russia scrapped a contract to supply Iran with S-300 surface-to-air missiles under Western pressure in 2010, and Iran later filed a $4-billion international arbitration suit against Russia in Geneva, but the two countries remain allies.
Russia provides a transit route for U.S. and NATO military cargo to Afghanistan, a facility that will become less important once most of the troops in the U.S.-led coalition leave in 2014.
Syria has accepted the Russian proposal to hand over chemical arms, but U.S. President Barack Obama said it was too early to tell if the initiative would succeed. He said he would keep military forces at the ready to strike if diplomacy fails.
Pushkov, who backs Putin but is not a policy maker, said that "the party of war in the United States will try to derail the Russian plan, and that has already begun ...
"The United States State Department has already been making skeptical statements.
Pushkov added: "An attack on Syria could cause a major regional war. Such a threat exists."
Russia has been a staunch supporter of Syrian President Bashar al-Assad in the more than two-year-old conflict with rebel forces, which has killed more than 100,000 people.
Washington and its allies accuse Assad's forces of launching a gas attack against rebels on August 21, which Washington says killed more than 1,400 people in rebel-held areas.
Assad denies the accusation, and Moscow says the rebels could have carried out the attack.
(Reporting By Alexei Anishchuk; Editing by Kevin Liffey)