US Secretary of State Mike Pompeo blamed Iran for the "unprovoked attacks", saying Washington made its assessment based on intelligence about the type of weapons used.
Iran's UN Mission said in a statement released on Friday that the government "categorically rejects" the US claim that it was responsible for the latest incidents against oil tankers which it condemns "in the strongest possible terms", state-run IRNA news agency reported.
It said "Iran stands ready to play an active and constructive role in ensuring the security of strategic maritime passages as well as promoting peace, stability and security in the region."
The Mission warned of "the US coercion, intimidation and malign behaviour" and expressed concern "over suspicious incidents" involving the two tankers.
It called on the international community to prevent "the reckless and dangerous policies and practices of the US and its regional allies in heightening the tensions in the region".
"The Islamic Republic of Iran reiterates that the only solution to the tension in this region is the active and constructive engagement of all regional countries within the context of a genuine dialogue based on mutual respect and basic principles of international law," the Mission said.
The Iranian Mission dismissed as "inflammatory" acting US Ambassador Jonathan Cohen's statement after a closed UN Security Council meeting on the tanker attacks that Tehran should meet Washington with diplomacy - "not with terror, attacks on ships, infrastructure and diplomatic facilities".
The US military's Central Command released a video that it said showed Iran's Revolutionary Guard "removing (an) unexploded limpet mine" from the side of the Kokuka Courageous following the blasts, reports said.
The incident came a month after four oil tankers were damaged in an attack off the United Arab Emirates. Washington at the time blamed Iran, but Tehran denied the accusations.