OPEC and non-OPEC producers will hold a meeting in the Qatari capital on April 17, the Qatari energy minister, who is also the current OPEC president, said on Wednesday.
"This comes as a follow-up to the meeting that was held last month in Doha between Qatar, Saudi Arabia, Russia and Venezuela at which they proposed an accord to freeze oil output at January 2016 levels and called on other producers to do so," the minister, Mohammed Bin Saleh Al-Sada, said in a statement.
The statement said that to date, around 15 OPEC and non-OPEC producers, accounting for about 73 percent of global oil output, are supporting this initiative.
On Monday, Russian Energy Minister Alexander Novak said after talks in Tehran that a deal could be signed in April and exclude Iran, which has the right to boost output after years of sanctions.
Kuwait, for example, has been arguing that all major producers need to be part of the output freeze.
While an exemption for Iran is not ideal, it is not a deal-breaker, OPEC sources said.
"It's a setback but it will not necessarily change the positive atmosphere that has already started," said one OPEC source from a major producer, referring to Iran saying it will not join any freeze accord.
"There are still talks about a possible meeting between main producers," the source said.
Brent crude was trading just under $39 a barrel on Wednesday, up from a 12-year low of $27.10 reached in January.
A preliminary deal to freeze output at January levels, reached last month by Saudi Arabia, Qatar and Venezuela plus non-OPEC member Russia, has helped to support prices.
A second delegate from the Organization of the Petroleum Exporting Countries said not having Iran in the pact was not the perfect outcome but it was not the worst.
"If the others freeze and the Iranians are outside the agreement, it will not help the market unless the demand is very large," this delegate said. "January output is already at high levels."
Three OPEC sources told Reuters on Monday that OPEC and non-OPEC producers were likely to meet in mid-April in Doha.
"You can't ignore all other oil producers. The meeting is likely to go ahead," a third source said, adding that the April meeting is likely to discuss and finalise the details of the freeze deal. "We will not just meet for the sake of meeting."
It was not clear which countries besides the original four would attend.
Kuwait and the United Arab Emirates have both said they would also commit to the freeze if other major producers did, but they have not received an invitation yet.
The willingness of Iraq, the biggest source of OPEC supply growth in 2015, to join the deal is also important. Baghdad on Monday said the freeze initiative was acceptable, citing the hardship for producers caused by low prices.