Quoting unnamed US officials, The Wall Street Journal reported that the US is especially worried about a fleet of speedboats controlled by the Islamic Revolutionary Guard Corps, Tehran's elite military force.
"The high-performance boats, which can be equipped with missiles, regularly challenge US and allied warships that transit through the Persian Gulf," the report said.
In recent months, a British destroyer fired warning shots at one of these boats as it appeared to be preparing to ram the larger ship, it said, adding Iranian aircraft have also challenged US ships in recent months.
"Iran seems to be aggressively defensive," it quoted a US official, who studies Tehran's military tactics, as saying.
Fearing that a misunderstanding could lead to wider conflict, US officials are considering a formal proposal for emergency communications, it said.
"At least initially, US defence officials are most enthusiastic about expanding navy-to-navy contacts with Iran to prevent miscalculations. But they remain wary of any direct engagement with the Islamic Revolutionary Guard Corps, due to its deep ties to Middle East militant groups," the paper said.
It isn't clear if the hotline proposal has been informally raised with Iran, possibly through Iraq, it said.
The White House also declined to comment on the issue. A senior defence official said discussion of the hot line was "very premature" and that no formal proposals have been presented to Secretary of Defence or President.