Syrian army tanks are seen deployed in the Jobar neighbourhood of Damascus on August 24, 2013. (STR/AFP/Getty Images)
WASHINGTON (NBC News) -- Missile strikes against Syria could be launched "as early as Thursday," senior U.S. officials said Tuesday as the White House intensified its push toward an international response to the suspected use of chemical weapons.
The "three days" of strikes would be limited in scope, and aimed at sending a message to Syria's President Bashar Assad rather than degrading his military capabilities, U.S. officials told NBC News.
RELATED | Kerry: Syria's use of chemical weapons 'undeniable'
News on the possible timescale for military action followed another round of telephone diplomacy by President Barack Obama and his administration.
Obama held discussions with Australian Prime Minister Kevin Rudd and French President Francois Hollande on Monday, while Secretary of State John Kerry spoke to U.N. Secretary General Ban Ki-moon in addition to political leaders in Britain, France, Jordan Turkey, Saudi Arabia, United Arab Emirates and Qatar.
British Prime Minister David Cameron recalled his country's Parliament from vacation on Tuesday and said lawmakers would vote Thursday on a proposal for action.
Defense Secretary Chuck Hagel told the BBC that the U.S. military was" ready to go" with any action ordered by the White House.
A U.N. team of inspectors, which is in Syria seeking evidence of Assad's use of chemical weapons, isn't scheduled to leave the country until Sunday.
The U.S. officials reiterated that any military action would not aim to kill Assad and would be limited because the goal would be to respond to the use of chemical weapons. Command and control bunkers, airfields and artillery would be targeted.
Kerry used unusually forceful language in a statement to reporters Monday, saying images that have emerged a suspected poison gas attack on Wednesday - of entire families' being killed without shedding a drop of blood, of bodies' contorting in spasms - "shock the conscience of the world."
He said there was "undeniable" evidence that Syria's government had used chemical weapons to kill its own people, adding that "there must be accountability" for what he termed a moral obscenity."
He spoke hours after the U.N. team was deliberately targeted by sniper fire.
"Our sense of basic humanity is offended not only by this cowardly crime but also by the cynical attempt to cover it up," Kerry said.
The rebel Free Syria Army's top general, Salim Idris, said Tuesday that air strikes were needed to stop Assad from launching more chemical attacks.
"If there is no action, we are afraid that in the coming days, not coming weeks, Bashar will use chemical weapons and chemical materials against very wide areas and, I'm afraid, to kill maybe 20,000 or 30,000 more people," he told NBC News' Chief Foreign Correspondent Richard Engel.
Some U.S. allies, most notably Britain, have signaled that a quick, limited military strike on Syria could take place without U.N. Security Council approval. However, Russian Foreign Minister Sergei Lavrov warned that such a move would be "a very grave violation of international law."
China also said an attack on Syria would be "dangerous and irresponsible."
"It is imperative that the United States and like-minded countries refrain from hasty armed invention and let the U.N. play its due part in determining how to act," the state-run Xinhua news agency said Tuesday.
Separately, the U.S. postponed a previously-planned meeting with a Russian delegation scheduled for this week at The Hague. The meeting had been due to discuss a possible international peace conference on Syria.
Russian Deputy Foreign Minister Gennady Gatilov said the postponement was "regrettable," according to Reuters.
Meanwhile, North Korea tried to export gas masks to Syria but they were seized in Turkey along with arms and ammunition, a Japanese daily newspaper reported on Tuesday.
A Libya-registered vessel, identified as Al En Ti Sar, left North Korea for Syria earlier this year with the consignment, the Sankei Shimbun said quoting unnamed sources from the U.S. military, Japanese and South Korean intelligence.
The vessel searched in April by Turkish authorities, who had been tipped off by the U.S. Officials seized 1,400 rifles and pistols and some 30,000 bullets as well as gas masks apparently for chemical protection, the newspaper said.