Iran has proposed a new package of proposals during talks in Baghdad over its disputed nuclear programme.
Iran, the US, Russia, China, Germany, France and Britain are holding a second meeting since diplomacy resumed in mid-April after a 15-month hiatus during which tensions soared.
Around 15,000 Iraqi police and troops will protect the venue inside Baghdad's heavily fortified Green Zone.
Tehran's suggestion of a meeting in troubled Iraq, whose leadership is friendly to Iran, was seen by some diplomats as testing a Western commitment to seeking a deal.
An EU spokesman refused to elaborate on the contents of the new proposals, but said they focused on addressing Western concerns about Iran's high-grade uranium enrichment activities.
Iran's state news agency said the proposals laid out by Iran were "comprehensive", unlike those of the P5+1, which it described as "nit-picking". Iranian negotiators expect world powers to respond to its proposals at the next session, it reported.
The US and its allies suspect Tehran is trying to develop a nuclear weapons capability and have imposed tough sanctions on Iran's energy and financial sectors.
Iran has long stated that its activities are purely peaceful, and says it wants the meeting to address the issue of sanctions with a view to rolling some of them back.
European Union members states are set to introduce a total embargo of Iranian crude oil purchases in July.
Diplomats say that potentially persuasive measure will not be cancelled unless Tehran takes substantial and demonstrative steps to curb its nuclear activities.