"China has agreed to changes proposed by Iran's central bank, raising its share in Iranian projects to more than $52 billion (42 billion euros)," deputy energy minister Esmail Mahsouli was quoted as saying by the Mehr news agency.
The decision follows a visit by central bank president Valiollah Seif to Beijing in September.
Iranian media cited officials as saying the investment will be guaranteed by Iranian deposits worth $20 billion held in Chinese banks due to international sanctions imposed for Iran's nuclear programme.
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Faced with tough international financial penalties, Iran has turned in recent years to China, Russia and Turkey to finance major projects.
"Government projects in the energy sector -- including water, electricity, oil, gas and petrochemical -- and others in the construction and industrial sectors, will receive Chinese financing," Mahsouli said.
He added that $1.5-$2 billion will be allocated to water and electric projects.
In previous statements, former deputy oil minister Ali Majedi said that China would finance industrial petrochemical projects to the tune of up to $4.5 billion.
Tehran and the P5+1 group of nations, which includes China, have until November 24 to reach a permanent deal on Iran's nuclear programme.