“This agreement cannot be implemented if one of the participants unilaterally steps out of it,” Lavrov told a news conference at the UN.
“It will fall apart and there will be no deal then,” he said, adding: “I think everyone understands that.”
Trump last week agreed to again waive US nuclear-related sanctions on Iran, but demanded that US lawmakers and European allies fix the “disastrous flaws” in the deal or face a US exit.
“This is a decisive moment,” Lavrov said.
Russia and the US are among the six world powers that signed the 2015 landmark deal with Iran that aims to curb Tehran’s nuclear program in exchange for lifting sanctions.
Lavrov made clear that there would be no attempt by Russia to salvage it with the five remaining powers, if the US pulls out.
Russia will make every effort to persuade the United States “not to touch this thing,” said Lavrov, saying that the deal was “not dead yet.”
The foreign minister again made the argument that killing off the Iran nuclear deal would also compromise any bid to persuade North Korea to scrap its nuclear arsenal.
If the Iranian nuclear deal is not upheld, “how can we ask North Korea to use the same option” and abandon its nuclear ambitions, asked Lavrov.
UN Secretary-General Antonio Guterres told the Security Council this week that it was in the world’s interest that the nuclear agreement “be preserved.”
Meanwhile, Lavrov also said that the US decision to withhold funds for a UN agency that assists Palestinians would seriously undermine efforts to meet the needs of refugees.
“This decision ... undermines in a serious way the efforts to satisfy the needs of Palestinian refugees in the region,” Lavrov said through a translator. “We’ll consult all stakeholders and we’ll see what we can do.”
The United States said this week it had decided to pay the UN Relief and Works Agency $60 million but was putting a hold on another $65 million it had been expected to offer. The US State Department also said it would not provide an additional $45 million in food aid it had pledged for Palestinians.