Nomura's chief political analyst warned of a "one-off" strike by the U.S. and its allies against the regime in Syria if evidence supports claims that Bashar al-Assad's government used chemical weapons last week in an attack outside Damascus.
Washington and its western allies will likely refrain from the type of engagement that characterized their 2011 action in Libya, Nomura's Senior Political Analyst Alastair Newton said in a report on Monday.
Instead, "we think that a relatively short series of surgical air and missile strikes against key regime installations and ordnance is the more likely option," representing a "warning shot" against the regime, Newton said.
In the most forceful U.S. reaction yet to last week's gas attack outside Damascus, U.S. Secretary of State John Kerry said President Barack Obama "believes there must be accountability for those who would use the world's most heinous weapons against the world's most vulnerable people," Reuters reported.
Military action, however, is still far from certain. A decisive factor is whether United Nations' chemical weapons inspectors in Syria can prove if al-Assad's regime was responsible for last week's attack. Doing so would constitute a breach of Obama's so-called "red line" and is likely to trigger a tough response.
"A decision to launch a military strike of some sort (or not) is likely to await at least a preliminary report from the U.N. team," Newton wrote.
(Read more: Obama weighs up options after Syria gas attack)
Expectations that Syria ally Russia will likely veto military action against Damascus – if authorization is sought from the U.N. Security Council – may not necessarily stop intervention from taking place since foreign ministers from both Britain and Turkey have publicly stated that action could be taken outside the U.N. system.
On balance, global oil markets – which are most prone to an escalation of the Syria crisis – will have several days to adjust to the risk of a possible military strike against Syria though there is unlikely to be any direct impact on supply since the country only produces negligible volumes of oil and natural gas, Newton said.
(Read more: Is a spike in oil prices around the corner?)
Still, Western military intervention will deepen regional tension, adding to the increased upward pressure on the price of Brent crude seen since the immediate aftermath of July's military coup in Egypt, according to Nomura.
"With Brent already at around $111 per barrel, this reinforces our existing view that perceived political risk in the MENA (Middle East and North Africa) region is likely to see a price move thorough 2013 Q3 and Q4 into the upper end of the $105-120 range where it has been for most of the past two-and-a-half years since civil war first broke out in Libya," Newton said.
A major risk factor is how Syria backer and regional power Iran would respond to a punitive Western strike against Syria.
- By CNBC's Sri Jegarajah. Follow him on Twitter: @cnbcsri