Tehran's foreign ministry spokesperson Saeed Khatibzadeh on Saturday said Iran and China are to sign a 25-year cooperation agreement later Saturday, as the US rivals move closer together.
China is Iran's leading trade partner and was the biggest buyer of Iranian oil before then US President Donald Trump reimposed sweeping unilateral sanctions in 2018 after abandoning a nuclear agreement with Tehran.
The pact, which will include "political, strategic and economic" components, will be signed by visiting Chinese Foreign Minister Wang Yi, who arrived in Tehran late Friday, Khatibzadeh told state television.
"We believe this document can be very effective in deepening" Iran-China relations, the spokesperson said, recalling that the pact had first been proposed during a visit to Tehran by Chinese President Xi Jinping in January 2016.
Xi and his Iranian counterpart Hassan Rouhani agreed then to establish a roadmap for "reciprocal investments in the fields of transport, ports, energy, industry, and services."
"Iran's government and people are striving as they always have to broaden relations with trustworthy, independent countries like China," supreme leader Ayatollah Ali Khamenei said at the time, describing the proposed cooperation agreement as "correct and reasonable".
A signing ceremony hosted by Iranian Foreign Minister Mohammad Javad Zarif is set for midday.
In July last year, controversy erupted over the proposed deal after former president Mahmoud Ahmadinejad charged that negotiations were being held for a "new, 25-year agreement with a foreign country" without the knowledge of the Iranian people.
The foreign minister was heckled in parliament when he assured lawmakers there was "nothing secret" in the proposed deal, which he promised would be publicly announced, "once it has been finalised".