The government is describing the deployment as an “investigation and research” mission. The participating forces are not authorized to use weapons to protect other ships against attack, the cabinet office said.
However, if the situation warrants, the mission could be converted to a “maritime policing operation,” a designation that would allow the destroyer and planes to defend other vessels.
The Maritime Self-Defense Force will not patrol the vital shipping lanes that run through the Strait of Hormuz. Analysts said that decision was meant to avoid giving the impression that Japan was taking sides with the United States against Iran, with which it has long maintained friendly relations.
The June attack on the Japanese-operated tanker in the Gulf of Oman occurred while Mr. Abe was on an official visit to Iran. The United States blamed the attack on Iran’s Islamic Revolutionary Guards Corps, which the Americans have labeled a terrorist organization.
Japan has been careful to keep up good relations with Iran, and Mr. Abe has positioned himself to act as a possible intermediary between Tehran and Washington.
Mr. Abe briefed Mr. Rouhani on Japan’s mission to the Middle East during their meeting last week, according to NHK, the Japanese national broadcaster. He also encouraged Mr. Rouhani to adhere to Iran’s commitments under the 2015 agreement that froze its nuclear program.
Iran has been incrementally reducing its commitment to the agreement as it seeks relief from heavy economic sanctions imposed on the country by Mr. Trump, following his decision to withdraw the United States from the pact.
Analysts say that Mr. Rouhani’s Japan trip was meant to signal a willingness to reopen long-stalled talks with Washington over Iran’s nuclear program.