Tehran has yet again threatened to close the Strait of Hormuz, a key passageway for shipments of oil from the Persian Gulf, as the US seeks to squeeze Iranian oil exports.

Iranian President Hassan Rouhani gave the warning on Tuesday, following comments from the US that sanctions have already succeeded in cutting Iranian oil exports. Sanctions on crude exports from the country were re-imposed early last month, but waivers were issued to the largest buyers of the country’s oil.

“The US should know that we are selling our oil …. and it is not able to stop Iran’s oil exports,” Rouhani was quoted as saying by S&P Global, citing Iranian state-run media. “And it should know if it intends to block our oil someday, no oil will be exported through the Persian Gulf.”

US Special Representative for Iran, Brian Hook, dismissed the threat, which has been made by Rouhani in the past.

“The strait is an international waterway. The United States will continue to work with our partners to ensure freedom of navigation and the free flow of commerce in international waterways,” Hook said, according to the Associated Press news agency.

Meanwhile, the US has sent an aircraft carrier strike group to the Persian Gulf, marking the end to a six-month absence of such a presence in the waters, The Wall Street Journal reported.

The USS Theodore Roosevelt, the last carrier strike group in the Gulf, was deployed to the Asia Pacific in March as part of a realignment away from the Middle East to confront China.