German Chancellor Angela Merkel on Wednesday held a rare telephone call with Iranian President Hassan Rouhani in which she voiced her "concern" over Tehran's non-compliance with the 2015 nuclear pact, her spokesman said.
"She expressed her concern that Iran continues to fail to meet its obligations under the nuclear agreement," spokesman Steffen Seibert said in a statement.
The chancellor also said that "now was the time for positive signals that create trust and increase the chances of a diplomatic solution", he added.
The call came on the eve of crunch talks between three European countries and the United States on how to salvage the deal aimed at reigning in Iran's nuclear programme.
French Foreign Minister Jean-Yves Le Drian will host his German and British counterparts in Paris, with America's new top diplomat Antony Blinken joining via videoconference, the French foreign ministry said.
The three European signatories to the deal want to revive the agreement that former US president Donald Trump walked away from in 2018.
The administration of Trump's successor Joe Biden has said it could rejoin if Tehran returns to compliance.
Analysts have said that only a small window of opportunity remains to save the deal and world powers will have to act fast.
The West is concerned that violations of the accord mean Iran is moving faster towards having the "breakout" capacity for building an atomic bomb, while Iranian presidential elections in June add a major risk factor.
The Joint Comprehensive Plan of Action (JCPOA) was based on Iran providing safeguards that it would not make an atomic bomb, in exchange for a gradual easing of international sanctions.
But the return of sanctions after Trump left the deal prompted Tehran to retaliate by intensifying its nuclear work in repeated violation of the deal.
The UN nuclear watchdog said last week Iran had started producing uranium metal in a new violation of the accord, prompting the European powers to warn Tehran risks losing the chance of seeing the full benefits of the deal.
President Rouhani has said that if sanctions are lifted, Iran will need only "a few hours" to verify the move and "then we will return to our commitments".