US warships in the Mediterranean remain ready to "strike hard" against the Syrian regime if ordered by President Barack Obama, the Navy's top civilian said on Wednesday.

Even as Washington put off possible military action against Damascus to pursue a last-ditch diplomatic solution, comments from Navy Secretary Ray Mabus provided a reminder that American destroyers equipped with cruise missiles are still in place in the eastern Mediterranean with no orders to leave.

"Two weeks ago, when new and horrifying images from Syria flashed across our televisions and streamed across our iPads, the US Navy and Marine Corps team was already there, in the Mediterranean and the waters of the Middle East," Mabus said in a speech at the National Defense University.

"I guarantee you that if we are called upon to strike, we will strike hard and we will strike fast," Mabus said.

He spoke a day after Obama delivered a televised address to the country arguing for "limited" military action if President Bashar al-Assad's regime refuses to give up its chemical weapons arsenal.

"As the president said last night, it (the attack) will be targeted and it will degrade the Assad regime's capabilities," Mabus said.

The Navy secretary's remarks underlined that naval forces will be at the forefront of any US attack on Syria, which is expected to rely mainly on Tomahawk missiles launched from vessels at sea.

Four US destroyers armed with cruise missiles were deployed to the eastern Mediterranean after the Syrian crisis escalated, as Obama weighed possible punitive strikes over an alleged chemical weapons attack by the Assad regime. An aircraft carrier strike group, including the carrier USS Nimitz along with warships armed with Tomahawks, was also sent to the Red Sea and is still there.

Defense Secretary Chuck Hagel meanwhile phoned the commander the USS Barry, one of the four guided-missile destroyers deployed to the Mediterranean, to thank the crew for staying at sea beyond their scheduled tour, the Pentagon said in a statement.

"Secretary Hagel thanked Commander (Tom) Dickinson and his sailors for their service during this period of heightened readiness," it said.

In his speech, Mabus cited the Navy's role in the confrontation with Syria as an example of the value of America's vast naval forces.

"We didn't have to surge forces. We didn't have to surge equipment. We didn't have to escalate the situation. The nation had immediate options because of our immediate presence," Mabus said.

"We reassure our partners that we are there, and remind those who may wish our country and allies harm that we're never far away. That is American seapower."

But he warned that "mindless" automatic budget cuts and political stalemate in Congress threatened to undermine America's naval reach.

He said that "if Congress fails to act to correct course there is the potential to seriously diminish and permanently harm America's indispensable maritime forces endangering not just our country but the world."

Within 12 to 18 months, sailors and US Marines will deploy without necessary training, Mabus said, opening the way to what he called a "hollow force."

Syria strikes on hold as world waits for Assad to act
Paris (AFP) Sept 11, 2013 - France on Wednesday joined the United States in putting threatened military action against Syria on hold as the world waited for Bashar al-Assad's regime to act on its pledge to give up its chemical weapons.

President Barack Obama on Tuesday asked US lawmakers to delay a vote on whether to authorise strikes against Syria to allow Russian-led attempts to broker a handover of Syria's arsenal time to bear fruit.

Obama said he would stay in close touch with Russia's President Vladimir Putin and would dispatch Secretary of State John Kerry to Geneva for talks on Thursday with his Russian counterpart.

"It's too early to tell whether this offer will succeed, and any agreement must verify that the Assad regime keeps its commitments," Obama warned in an address to the nation from the White House.

"But this initiative has the potential to remove the threat of chemical weapons without the use of force, particularly because Russia is one of Assad's strongest allies."

The switch to diplomacy was welcomed on Wednesday by China, which also praised Syria's offer to sign an international treaty banning chemical weapons.

"We hope all relevant sides can grasp this opportunity to solve the Syria problem through diplomatic and political means," a foreign ministry spokesman said.

France aligned itself with the US position of insisting that the threat of airstrikes remained in place but that the diplomatic process would be given time to produce results.

"France will remain, in permanent contact with its partners, mobilised to punish the use of chemical weapons by the Syrian regime and to deter them from using them again," President Francois Hollande said after talks with his military chiefs.

Amongst Western leaders, Hollande has been the leading advocate of intervention in Syria, although, like Obama, he has been unable to convince a majority of his electorate of the case for action.

The French warning that the diplomatic route would not be pursued indefinitely without clear signs of progress echoed Obama's statement that US cruise missile destroyers would remain in place within striking distance of Syria.

"The US military doesn't do pinpricks," Obama said. "Even a limited strike will send a message to Assad that no other nation can deliver."

France and the United States had threatened strikes in response to the use of sarin gas in an August 21 attack on rebel-held suburbs of Damascus. Both allies say they have proof the attack, which the US says killed more than 1,400 people, was carried out by Assad's forces.

Obama said allowing a dictator to get away with such acts would threaten US security, but he assured his listeners that there would be no military action until UN inspectors had delivered a report into what happened.

Syria announced on Tuesday that it would join an international convention banning chemical weapons, which it had previously denied having.

Syria is one of only seven UN member states not already party to the 1993 "Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction."

Signatories are supposed to destroy any chemical weapons under their control and to allow UN inspectors access to their sites. Russia has offered to oversee this process and has said talks with the Syrians on how to go about it are already underway.

The path to a peaceful resolution of the crisis remains littered with obstacles however with the US, France and Britain still at odds with the Russians over the next steps.

Putin, a key Assad ally, has warned that Syria cannot be expected to act with a gun pointed at its head.

"It is difficult to constrain Syria or another country to disarm unilaterally while military action against that country is being prepared," the Russian leader said.

France and Britain are pushing for a UN Security Council resolution authorising military action in the event of Syria failing to act on its disarmament promises. Russia has made it clear it will veto any ultimatum of that kind and is likely to be able to count on backing from China, a fellow permanent member of the Security Council.

Syrian opponents of the Assad regime have warned that the chemical weapons negotiations will do nothing to end a conflict in which over 110,000 people have died in more than two years of fighting.

UN human rights investigators on Wednesday reported that the conflict had been characterised by widespread war crimes, mostly committed by regime forces. The team was unable to reach any conclusions on the use of chemical weapons, which is being investigated by a different group of experts.