Xi discussed cooperation with leaders of Saudi Arabia, Egypt and Iran within the framework of the Belt and Road Initiative and unveiled cooperation projects in fields including industrial capacity, infrastructure and energy.

Iranian President Hassan Rouhani said he and Mr Xi had signed a "comprehensive 25-year document" on strategic relations.

Khamenei said Iran won't forget China's support at the time of sanctions.

The consensus was reached during President Xi Jinping's visit to Iran, the first in 14 years by a Chinese head of state.

Chinese president for his part said he has traveled to Iran to prepare the ground for a new prospect in relations between the two countries. China, the world's second-largest economy, also relies heavily on energy imports from the Middle East. Beijing is Tehran's top customer for oil exports, which in recent years were hit by U.S. and European Union sanctions over Tehran's nuclear program. "Iran and China have agreed to increase trade to $600 billion in the next 10 years", Rouhani said at a news conference with Xi, which was broadcast live on state television.

Iranian Green Movement activists launched campaigns on social networking media promising the current government with their return to streets to recapture the protests of 2009, especially after the Guardian Council taking the decision of putting out most of the reformist candidates for the February Islamic Consultative Assembly and the Assembly of Experts elections.

The first leg of Xi's Middle East tour took him to Saudi Arabia, where he met with King Salman bin Abdulaziz Al Saud on Tuesday.

"We discussed security cooperation to help countries such as Syria, Yemen and Afghanistan, which are at risk".

The Chinese president is set to meet with Iran's spiritual leader, Supreme Leader Ayatollah Ali Khamenei, later on Saturday. Xi Jinping, visiting Iran just days after the lifting of worldwide sanctions under a historic nuclear deal, said he hopes for a "new chapter" in relations.

In Cairo, Xi offered $55 billion in loans and investments to the Middle East, a region where China wants to strengthen its economic presence.

"Iran is the most reliable country in the region for energy since its energy policies will never be affected by foreigners", Khamenei was quoted by his official website as saying at a meeting with Xi. "A statement on both sides should also take this opportunity in order to further upgrade mutual exchanges at different levels and further boost the political trust between the two countries", Xi said.

"The United States remains concerned about some of the activities that Iran is engaged in other countries", Kerry told reporters, citing as an example Iran's "support for terrorist groups like Hezbollah" in Lebanon.