By Susan Cornwell
WASHINGTON (Reuters) - President Barack Obama has several diplomatic and military choices before him as he considers whether to take action against the government of Syrian President Bashar al-Assad over charges it carried out a massive deadly chemical weapons attack in the civil war there.
Here are some of Obama's options, and the downside of taking them:
* PUSH FOR U.N. INSPECTORS TO GET ACCESS TO THE SITE OF THE ALLEGED CHEMICAL ATTACKS.
This is currently a major focus of the United States and its allies. U.N. Secretary-General Ban Ki-moon asked the Syrian government on Thursday to allow U.N. inspectors in Syria to investigate this week's alleged chemical attack in which hundreds were reported to have died. The inspectors already are in Syria to probe previous charges of chemical weapons use by Assad's government. Obama also has directed the U.S. intelligence community to look into the matter.
Russia, a member of the U.N. Security Council and ally of Assad, suspects any chemical attack may have been staged by Syrian rebels opposed to Assad, and has urged an investigation. Mona Yacoubian, a Middle East adviser at the Stimson Center in Washington, said the United States should be trying to get the Russians on board "with some kind of Security Council resolution demanding or impelling this (U.N.) team to be able to investigate."
The Russians could also leverage their influence with their Syrian allies to let the U.N. team in, she said.
U.N. inspectors are charged with trying to establish whether chemical weapons were used, not determine who used them. So even if they do investigate this week's suspected chemical attack, their eventual findings would not necessarily help the United States establish firmly who was to blame, the presumed prerequisite for action.
* SEEK ACTION BY THE U.N. SECURITY COUNCIL, SUCH AS SANCTIONS, ON SYRIA.
"If the reports are validated, the United Nations Security Council must condemn the attack in the strongest possible terms and take immediate actions, to include the imposition of sanctions, to prevent further atrocities by the Assad regime," Senator Robert Menendez, a Democrat and chairman of the Senate Foreign Relations Committee, said on Thursday, echoing the sentiments of several lawmakers in Washington.
Russia could block such an action by the Security Council.
* ACCELERATE EFFORTS TO HOLD AN INTERNATIONAL PEACE CONFERENCE ON SYRIA.
Russian and U.S. officials are expected to meet in The Hague on Wednesday to discuss plans for such a conference.
Moscow and Washington have been trying since May to organize such a gathering but it has not happened, partly because Syrian rebel factions cannot agree on who should represent them.
* PROVIDE MORE MEDICAL ASSISTANCE AND TRAINING TO SYRIAN REBELS.
So far the United States has provided the rebels with some training, medical kits and food. Last month congressional aides told Reuters that about $27 million had been spent to train hundreds of rebels in neighboring countries. The United States could provide chemical weapons suits and gas masks to rebel forces.
This is basically more of what the United States has been doing, so it's unclear if it would change much in an uprising that is two years old.
* ARM THE SYRIAN REBELS.
The White House said on June 13 that it had concluded that Assad's forces used chemical weapons and that Obama had decided to send military aid to the opposition. But the rebels say that so far, no weapons have arrived. Rebel sources say they still hope the administration will at least send them small arms and ammunition. They also would like anti-tank weapons and shoulder-fired missiles.
Even advocates of arming the rebels acknowledge that such weapons could end up in the wrong hands, and that providing them might not be enough to change the tide of the war even as it would get the United States more involved.
"We can work to build the capacity of the moderate opposition," Representative Eliot Engel, the ranking Democrat on the House of Representatives Foreign Affairs Committee and an advocate of arming the rebels, said this week. But, he added: "Until we are prepared to severely diminish the regime's ability to inflict harm upon its own citizens and even the playing field, such a moderate opposition stands little chance against the regime's (missiles), tanks and planes."
* SEIZE AND SECURE ANY CHEMICAL WEAPONS HELD BY ASSAD'S REGIME.
This action presumably would prevent their use, and prevent them from falling into the hands of extremist groups.
Analysts say it would be difficult because the weapons are believed to be in different places, and that securing them would mean the United States would have to put "boots on the ground" - an unpopular idea among Americans, polls show.
"It would involve a lot of ground troops, and we're not prepared to do that," said Andrew Tabler of the Washington Institute for Near East Policy. He called this is the "least likely" option.
* ORDER TARGETED AIR STRIKES FOCUSED ON SYRIAN MILITARY UNITS BELIEVED TO BE RESPONSIBLE FOR CHEMICAL WEAPONS ATTACK.
Such strikes would target Syrian military units believed to have committed chemical attacks and send a message that anyone using chemical weapons could expect to be targeted as well.
It might take some time to produce reliable intelligence on which Syrian military units should be held responsible, analysts say.
* ORDER AIR STRIKES AT ASSAD'S MILITARY AIRCRAFT, AIR BASES AND BALLISTIC MISSILE UNITS.
This is an option favored by Republican Senator John McCain, who says the Democratic president hasn't done enough to protect the Syrian people.
Elliott Abrams, a former Bush and Reagan administration official, said Assad's use of air power has been a huge advantage for the regime, and eliminating or weakening it would tilt the battlefield toward the rebels.
"To me, the arguments are stronger now for a strike at Assad's air assets and any elements of his military connected to the chemical attack. And I believe we would have wide European support and participation," Abrams said on Thursday.
This option may already have some powerful support. In a meeting of Obama's top national security officials on June 12, Secretary of State John Kerry said that the United States should go beyond arming opposition fighters and use air strikes, a person familiar with the talks said. Martin Dempsey, chairman of the Joint Chiefs of Staff, pushed back, arguing that such a mission would be complex and costly.
Dempsey said in a letter to Engel, the representative, this week that although the American military could destroy Assad's air force, doing so would pull the United States into the Syrian conflict without necessarily ending it.
"The loss of Assad's air force would negate his ability to attack opposition forces from the air," Dempsey said. "It would not be militarily decisive, but it would commit us decisively to the conflict."
* ESTABLISH A "NO-FLY" ZONE WHERE SYRIAN MILITARY AIRCRAFT COULD NOT GO.
This option, most vocally advocated by McCain, would use lethal force to stop Assad's regime from using planes to bomb rebels. It would involve neutralizing the regime's air defense system as well as shooting down Syrian planes.
"No-fly zones would not address the biggest of the killers: artillery," said Frederic Hof, a senior fellow at the Atlantic Council and former special U.S. representative on Syria.
It also would be very expensive, Dempsey said last month in a letter to Senate Armed Services Chairman Carl Levin, a Democrat.
"We would require hundreds of ground- and sea-based aircraft, intelligence and electronic warfare support, and enablers for refueling and communications," he said in the letter.
Dempsey estimated the cost would be "$500 million initially, (and) averaging as much as a billion dollars per month over the course of a year." He added that the U.S. military might lose some of its aircraft and pilots, "which would require us to insert personnel recovery forces."
* PUT U.S. TROOPS ON THE GROUND IN SYRIA.
No one in an official position in Washington is arguing for the United States to invade Syria in order to knock Assad out of power.
If the United States were to make such a move, the risks and costs listed above would come into play at dramatically higher levels - and the country would become a major player in another Middle East war.
(Additional reporting by Patricia Zengerle and Tabassum Zakaria; Editing by David Lindsey and Xavier Briand)