Tehran's oil exports have risen since late 2020, despite US sanctions toughened under US President Donald Trump. Joe Biden's administration took office in January pledging to rejoin Iran's nuclear deal with world powers, which Trump had quit.
"China and Iran are carrying out normal economic and trade cooperation, including energy, within the framework of international law, and the relevant cooperation is reasonable and legitimate," the spokesperson said.
The move would be the first under the management of General Joaquim Silva e Luna, who replaced Roberto Castello Branco as the company's top executive after the government apparently disagreed with the state-run company's fuel pricing policy.
In a note on Friday, brokerage Ativa Investimentos said its model indicated a potential 13% rise in gasoline prices, driven by the increasing international oil prices.
Demand will rise by 5.95 million barrels per day (bpd) in 2021, or 6.6%, the Organization of the Petroleum Exporting Countries forecast in its monthly report, up 70,000 bpd from last month.
OPEC raised its forecast of 2021 world economic growth to 5.4% from 5.1%, assuming the impact of the pandemic is "largely contained" by the beginning of the second half of the year.
The company, which had a debt pile of $39 billion at the end of 2020, had earlier expected to reduce its debt to $35 billion around the fourth quarter of 2021 or first quarter of 2022.
The London-based company said on Tuesday it expects sale proceeds in 2021 to be at the top end of its existing $4 billion to $6 billion range.
"Total oil demand is foreseen to reach 96.3 million bpd with most consumption appearing in the second half," OPEC said in the report.
"This year's demand growth will not be able to compensate for the major shortfall from 2020 as mobility is forecast to remain impaired throughout 2021."