"We have an international situation there in the Middle East...The focus for myself and Ambassador [John] Bolton and Secretary [Mike] Pompeo is to build international consensus to this international problem," Shanahan said.
Earlier in the day, US President Donald Trump claimed in an interview with Fox News that Iran was responsible for explosions that damaged two oil tankers sailing through the Gulf of Oman on 13 June.
Secretary of State Mike Pompeo was the first US official to blame Iran for allegedly attacking the oil tankers, although the cause of the explosions has not been determined yet.
Iran has denied the US accusations and called on Washington and its regional allies to cease their false flag operations, used to shift the blame onto Tehran.
On 13 June Norway's Front Altair and Japan's Kokuka Courageous oil tankers sailing through the Gulf of Oman suffered explosions that damaged their hulls and caused a fire. The incident follows a similar one in May, when four oil tankers near the UAE were damaged as a result of what Abu Dabi sees as an "act of sabotage".