War with Iran is the mother of all wars, Iranian President Hassan Rouhani said on Tuesday in a speech broadcast live on state TV, warning once again that shipping might not be safe in the Strait of Hormuz oil waterway.

Tensions have risen between Iran and the West since last year when the U.S. pulled out of an international agreement which curbed the Islamic Republic's nuclear program in return for an easing of economic sanctions on Iran.

"Peace with Iran is the mother of all peace, war with Iran is the mother of all wars," Rouhani said at the Foreign Ministry in a speech which also praised Foreign Minister Mohammad Javad Zarif after the U.S. imposed sanctions on him last Wednesday.

If the U.S. wants to have negotiations with Iran then it must lift all sanctions, Rouhani said, noting that Iran must be allowed to export oil.

"The Islamic Republic of Iran favors talks and negotiations and, if the U.S. really wants to talk, before anything else it should lift all sanctions," Rouhani said.

Iran was ready for talks regardless of whether or not the U.S. was party to a landmark nuclear deal. "Whether they want to come into the JCPoA or not, it's up to them," said Rouhani, referring to the 2015 nuclear deal known formally as the Joint Comprehensive Plan of Action. 

Fuelling fears of a Middle East war with global repercussions, the Guards seized British tanker Stena Impero near the Strait of Hormuz in July for alleged marine violations, two weeks after British forces captured an Iranian oil tanker near Gibraltar accused of violating sanctions on Syria.

"A strait for a strait. It can't be that the Strait of Hormuz is free for you and the Strait of Gibraltar is not free for us," Rouhani said.

Approximately one-fifth of the world's oil traffic passes through the strategic Strait of Hormuz.

On Sunday, the Guards seized an Iraqi oil tanker in the Gulf which they said was smuggling fuel and detained seven crewmen, Iran's state media reported.