"We had a first discussion of the next steps in the Security Council, following the lines of (Security Council) Resolution 1696," said another diplomat.
The so-called “next steps” call for possible sanctions if Iran defied, as it has, a call to suspend strategic nuclear fuel work.
Iran failed to meet an August 31 deadline, laid out in the resolution, to freeze uranium enrichment, which makes nuclear reactor fuel but also nuclear weapons grade material.
A report by the UN watchdog International Atomic Energy Agency makes clear that Iran hasn't met the requirements of the Security Council and the IAEA.
Halting enrichment is also the condition made by the six nations; permanent Security Council members Britain, China, France, Russia and the United States, plus Germany.
The made it a requirement for opening negotiations aimed at giving Iran trade, security and technology benefits in exchange for suspending it nuclear works.
Russia and China reluctant
The unidentified diplomat said the Berlin talks were "actually quite a productive meeting. There was common analysis on where we were."
He did not give details of what was discussed and stressed that "there is obviously more work that needs to be done. That work is going to continue next week."
Russia and China, both major trading partners with Iran, are reluctant to support sanctions, fearing they will worsen the current confrontation or even lead to war.
Another diplomat close to the talks said that US Under Secretary of State Nicholas Burns had "made a strong case for sanctions," saying the Security Council should take such action by the end of the month.
"But the Russians and Chinese want to go a bit slower," he said.
Specific measures were discussed from a list of graduated sanctions that begin with symbolic gestures such as limiting travel by Iranian nuclear scientists and progress towards widespread international economic bans.
The six nations will be closely watching a meeting planned for Saturday, probably in Vienna, between European Union foreign policy chief Javier Solana and top Iranian nuclear negotiator Ali Larijani to see if there is room for further discussion with the Iranians.
In Tehran, a national security council official said Mr Larijani wants to have "serious and constructive negotiations with the 5 plus 1 group ... especially on the nuclear question."
However, in a sign of mounting international impatience, Russian Foreign Minister Sergei Lavrov said Russia was considering support for Security Council economic sanctions against Iran.