Two U.S. officials said Iran launched drones near American ships, sent speedboats to mine the Strait of Hormuz and stepped up activity at some of its missile sites.
After the prime minister made the announcement, the Israeli military said it had struck more than 70 Hezbollah sites in the past day.
There is no shortage of targets should President Trump, in coordination with Israel, decide to resume the assault on Iran.
There is no shortage of targets if he decides to strike: Energy facilities left untouched, the deep underground nuclear storage site at Isfahan and missile sites that appear to have been dug out.
Decision making in the country is guided by a small group of men associated with the Islamic Revolutionary Guards Corps.
The warning was issued as President Trump and Vice President JD Vance say progress is being made toward a deal, while keeping open the threat of renewed strikes.
An Israeli strike designed to free Mahmoud Ahmadinejad from house arrest in Tehran, U.S. officials said, was part of an effort to bring about regime change and put him in power.
The charges against Mohammad al-Saadi in the United States have raised concerns that Iran could be working with its proxies to stage attacks outside the region.
Top aides have drafted battle plans as peace negotiations have stalled.
Vessels are traveling without transmitting critical information meant to keep the waters safe, maritime intelligence experts say.