The European Union (EU) cannot provide legal and economic guarantees to Iran after the United States pulled out of the 2015 nuclear accord, but is serious about seeking a way to keep investment flowing, the EU’s top diplomat said on Tuesday, according to Reuters.

After a meeting of the foreign ministers of Iran, Britain, France and Germany, EU foreign policy chief Federica Mogherini said the group will come forward with measures in the next few weeks after tasking experts to protect European business in Iran.

The group will meet again in Vienna next week at the level of deputy foreign ministers in a special format within the nuclear deal on Iran’s request and without the United States, which abandoned the accord last week.

On Wednesday, the European Commission will meanwhile discuss the EU’s 1990s-era blocking sanctions, Mogherini said. They might help shield European businesses from U.S. penalties but have never been used.

“We are working on finding a practical solution ... in a short delay of time,” Mogherini told a news conference, according to Reuters.

“We are talking about solutions to keep the deal alive,” she stressed, adding that measures would seek to allow Iran to keep exporting oil and for European banks to continue to operate.

“We have a quite clear list of issues to address. We are operating in a very difficult context ... I cannot talk about legal or economic guarantees but I can talk about serious, determined, immediate work from the European side.”

Iranian Foreign Minister Mohammad Javad Zarif said following Tuesday’s meeting, "I believe it's a good start. We're not there, we're beginning the process.”

But he warned that Tehran expected to see progress towards the guarantees it wants "within the next few weeks".

Iran’s Deputy Foreign Minister, Abbas Araghchi, earlier this week demanded that European countries provide “guarantees” within 60 days to safeguard Iran’s interests after the U.S. left the 2015 deal.

He also said that if Iran does not receive such guarantees European leaders would have to “take the necessary decisions”.

While Trump withdrew from the Iran deal and announced he would reimpose sanctions on Iran, the European Union did not follow suit, and said it would remain in the agreement and will do so “as long as Iran continues to implement its nuclear related commitments, as it is doing so far.”

On Sunday, French Foreign Minister Jean-Yves Le Drian said his country believes the deal can prevent Tehran from acquiring nuclear weapons.