The world can't live with major Gulf confrontation: UN chief
"It is absolutely essential to avoid any escalation of the situation," he told reporters.
Guterres said he has "no particular insight" into the possibility of a meeting between US President Donald Trump and Iran's President Hassan Rouhani.
But he said any effort to avoid a confrontation "will always be welcome".
Trump has repeatedly indicated he is ready to meet with Rouhani, who is expected to attend the UN General Assembly in New York this month.
However, the Iranians have so far not given a positive response.
On Wednesday, Rouhani blasted the Trump administration, which has poured pressure on Iran, saying "the Americans must understand that bellicosity and warmongering don't work in their favor. Both... must be abandoned."
Arch-foes Tehran and Washington have been at loggerheads since May last year when Trump withdrew from a 2015 nuclear deal and began reimposing punitive measures.
Iran responded by scaling back its commitments to the accord, which gave it the promise of sanctions relief in return for curbs on its nuclear program.
Follow us on Twitter: @The_NewArab