Iranian Foreign Ministry spokesperson Esmail Baghaei said an agreement with Oman on ship movements through the Strait of Hormuz was nearing completion.
He did not provide details of the prospective arrangement.
Baghaei said Iran and Oman had reached an understanding on the geographical coordinates of a route.
He said any agreement would not itself ensure safe navigation because US sanctions on Iranian ports were still disrupting security.
Baghaei also said Iran considered a naval blockade and other US actions against Iran and its interests to be continuing threats to security in the waterway.
Deputy Foreign Minister Kazem Gharibabadi said the proposed route would be temporary and could remain open for two to four months.
US officials said discussions on reopening the waterway by the end of the week were progressing, while Tehran has said it is not negotiating with Washington and has no plan to do so.
President Donald Trump said Iran would be severely harmed if the strait was not reopened very soon.
The strait carries roughly one-fifth of global oil and liquefied natural gas shipments, and the disruption to navigation has been associated with sharp oil-price swings.
A senior Iranian official was cited as saying Tehran wanted a 5% to 7% levy on cargo values for vessels using the strait; Oman was discussing about 3%, while Washington opposed any levy.
The terms of any agreement, the route’s operating rules and whether other parties will accept them remain unclear.