A senior German diplomat on Thursday flew out to convince Iran that it must continue to respect its nuclear deal with world powers.
Germany's Foreign Ministry sent its political director, Jens Ploetner, to Iran to meet deputy foreign minister Abbas Araghchi to try to salvage the nuclear deal signed in 2015 in Vienna.
The accord has steadily unravelled since the Trump administration pulled out, and reimposed and increased sanctions on Tehran last year.
Mr Araghchi demanded that European signatories follow through on their commitments under the deal, Iran's official Irna news agency reported.
Mr Ploetner said the European side would continue to strive to meet Iran's demands and save the deal.
The White House this month sent an aircraft carrier and B-52 bombers to the Gulf region over a threat it said had been made by Iran.
Tehran this month said that the remaining signatories to the deal – Germany, France, Britain, China and Russia – had two months to develop a plan that would protect Iran from American sanctions.
"There is a real risk of escalation, including through misunderstandings or an incident," the German Foreign Ministry said. "In this situation, dialogue is very important."
The ministry said there was still a "window for diplomacy to persuade Iran to continue its full compliance".
It said Germany remained in close contact with the other nations that have been struggling to keep the deal alive.
The accord, intended to keep Iran from developing a nuclear weapon, promised economic incentives in exchange for restrictions on Tehran's atomic and missile programmes.
Despite efforts so far to keep the deal from collapsing, Iran's economy has been struggling and its currency has plummeted after the reimposition of US sanctions.
Iran continued to abide by the terms of the deal, a February report by the International Atomic Energy Agency said.
But it expressed increasing frustration with the inability of the Europeans to provide economic relief. A new agency report is due out soon.
On Monday, Iran announced it had quadrupled its production capacity of low-enriched uranium.
Iranian officials said that the uranium would be enriched only to the 3.67 per cent limit set under the nuclear deal, making it suitable for a power plant but far below what is needed for an atomic weapon.
By increasing production, however, Iran will probably soon exceed the stockpile limits set by the nuclear accord, which would exacerbate the situation even further.
Several incidents have added to the crisis, including the sabotage of oil tankers off the coast of the UAE and a rocket that landed near the US embassy in Baghdad.
The US has blamed Iran for both incidents without offering evidence. America has also moved non-essential diplomatic staff from Iraq.
The Pentagon was to present plans to the White House on Thursday to send up to 10,000 more American troops to the Middle Eas, US officials said.
Iran has watched warily as the USS Abraham Lincoln heads towards the Strait of Hormuz and B-52 bombers begin flying missions in the region.
Iran's armed forces Chief of Staff, Gen Mohammad Bagheri, said on Thursday that the military would remain watchful about "deceptions by the US government and its adventurous" president.
"With the finger on the trigger, Iran is ready to respond to any invader strongly and with unbelievable speed," Gen Bagheri said.
Iran's Foreign Minister Javad Zarif was expected to arrive later on Thursday in Islamabad as Pakistan seeks to calm regional tension.
Mr Zarif was to hold talks with Pakistani officials on Friday.
"We believe the situation in the region is serious and needs to be addressed through dialogue by all parties," Pakistan's Foreign Ministry said.
"We expect all sides to show restraint, as any miscalculated move, can transmute into a large-scale conflict."
