Beijing has expressed hope that Friday's nuclear energy meetings will lead to resumed negotiations and dialogue.
In a joint statement, China, Iran, and Russia write that they "emphasize the need to end all illegal and unilateral sanctions".
The situation has reached a critical point, according to China's Foreign Minister Wang Yi.
Donald Trump has sent a letter to the Iranian government through a diplomat from the United Arab Emirates this week, which is said to be reviewed by Tehran.
Threatening Military Intervention
The content of the letter is unknown, but Donald Trump has, like Wang Yi, warned in recent days that the deadlock with Iran has reached a critical stage, and hinted that military measures may become necessary if a nuclear energy agreement is not concluded soon.
Iran's supreme leader, Ayatollah Ali Khamenei, has, on the other hand, given notice that no talks with the US will be held under pressure. The message was repeated by Foreign Minister Abbas Aragchi in a state interview on Thursday:
We will initiate direct negotiations when we have equal conditions, free from pressure and threats.
Ticking Clock
Instead, the US stepped up the "maximum pressure" policy against Iran on Thursday, which Trump introduced during his first term, and announced new sanctions against Iran's Oil Minister Mohsen Paknejad.
The clock is ticking for the US and Iran to reach an agreement. After Trump withdrew the US from the nuclear energy agreement with Iran and other major powers in 2018 and re-imposed sanctions, Iran has increased its stockpile of highly enriched uranium.
The development has accelerated in recent times, and in February, the UN's atomic energy agency IAEA reported that Iran has nearly 275 kilograms of uranium enriched to 60 percent. It is a short step from the 90-percent level required to manufacture nuclear weapons.
