By Barbara Starr

Although the U.S. focus remains on exerting diplomatic and economic pressure on Syria, the Pentagon and the U.S. Central Command have begun a preliminary internal review of U.S. military capabilities, CNN has learned.

The options are being prepared in the event President Barack Obama were to call for them. Two senior administration officials who spoke about the review to CNN emphasized that U.S. policy for now remains the use of non-military options.

The focus on diplomatic options was underscored by the U.S. ambassador to the United Nations in an interview with CNN on Tuesday.

"Before we start talking about military options, we very much want to ensure that we have exhausted all the political, economic and diplomatic means at our disposal," Ambassador Susan Rice said on CNN's “Situation Room with Wolf Blitzer.”

The president has also said that the U.S. is working on non-military options first.

"I think it is very important for us to try to resolve this without recourse to outside military intervention, and I think that's possible," Obama said in an interview with NBC News that aired during the Super Bowl on Sunday.

But the military is beginning to look at what can be done. One of the senior U.S. officials called the effort a “scoping exercise” to see what capabilities are available given other U.S. military commitments in the region.

Both officials pointed out that this type of planning exercise is typical for the Pentagon, which would not want to be in the position of not having options for the president, if and when they are asked for.

It would be Gen. James Mattis, head of U.S. Central Command, who would provide details on what U.S. military assets are available, what missions they could perform if asked, and what risks U.S. forces might face.

“The Pentagon is closely monitoring developments in Syria. It wouldn’t be doing its job if it didn’t put some ideas on the table,” one of the senior U.S. officials told CNN. “But absolutely no decisions have been made on military support for Syria.”

The two officials were not willing to be identified because they were not authorized to talk to the media.

Typically those types of options are held by the Pentagon as very preliminary plans and not even forwarded to the White House unless asked for. If asked, plans are then fleshed out with specific units to support them.

In this type of analysis being done, the military would typically look at all options ranging from humanitarian relief, to support for opposition groups, as well as outright military strikes, although that is an unlikely option, both officials said.

“This remains a campaign to apply economic and diplomatic pressure,” the first official said.

The military’s work to analyze potential military options for Syria has been quietly going on for several weeks, two administration officials confirm to CNN. The bulk of the analysis is being done by staff of General Mattis, who would be the senior commander if the President were to order any action.

Mattis’ analysis is being shared with General Martin Dempsey, chairman of the Joint Chiefs of Staff, who would then present options to the White House, if it came to that.

“We don’t want to be in the position of suddenly dusting off some five year old plan,” one official said. The official emphasized the work is extremely preliminary but said the military would look at a full range of contingencies.

Arizona Sen. John McCain, the top Republican on the Armed Services committee, told reporters Tuesday that the U.S. should consider "all options including arming the opposition."

But U.S. officials said that adding weapons into the volatile and violent situation is not a viable option.

"We never take anything off the table. The president does (or) doesn't. However, as the president himself made absolutely clear and as the secretary has continued to say, we don't think more arms into Syria is the answer," said State Department spokeswoman Victoria Nuland.