Saeed Jalili, Iran's chief negotiator, said participants at the Almaty, Kazakhstan, talks presented "more realistic proposals that come a little closer to Iran's position," The New York Times reported.
"Their proposals seem more realistic and positive," Jalili said, adding there have been "some changes in their viewpoint."
The two days of talks were called to get a clear response from Iran to an offer of gradual relief from sanctions in return for measures that inspire confidence about Iran's intent for its nuclear program, Western diplomats said.
The diplomats said the technical meeting in Istanbul, Turkey, would be to detail the proposals before returning to Almaty to listen to Iran's response.
The talks have been intermittent since they began in October 2009, with the last meeting eight months ago in Moscow.
As a first step, the six powers -- permanent U.N. Security Council members China, Britain, France, Russia and the United States, plus Germany -- want Iran to end uranium enrichment to 20 percent and to export its stockpile of more highly enriched uranium, which can turned into bomb-grade material more quickly, the Times said. The powers also want Iran to shutter its Fordo enrichment facility, which Iran so far has refused to do.
In return, the six countries have offered Iran sanctions relief, reportedly including permission to resume trading of gold and precious metals, as well as resuming some international banking activity and petroleum trading, the Times said.
The ultimate goal of the talks is to get Iran to comply with Security Council resolutions that it stop enrichment completely until it can satisfy the International Atomic Energy Agency, the United Nation's nuclear watchdog, that it has no weapons program and no hidden enrichment sites. In return, all sanctions, which have crippled Iran's economy, would be lifted.
Iran meanwhile, has created a plan B for nuclear weapons capacity in a second plant, satellite images commissioned by Britain's The Daily Telegraph indicated.
The IR-40 40-megawatt thermal nuclear reactor in Arak -- said by the regime of President Mahmoud Ahmadinejad to produce power and isotopes -- has begun heavy-water production.
The images, taken Feb. 9, show signs of activity at the Arak plant, 150 miles southwest of Tehran, including a cloud of steam analysts said indicates heavy-water production.
The images also show surface-to-air missile and artillery sites to protect the plant.
Western governments and the IAEA have privately had information about the Arak activity for some time, the Telegraph said.
Israel has warned it may carry out military strikes to stop Iran from gaining nuclear-weapons capacity. Washington says it won't rule out using force but prefers diplomacy.
Russian envoy Deputy Foreign Minister Sergei Ryabkov, a staunch opponent to increasing sanctions, said time is running out for the talks. Russia's Interfax news agency reported Ryabkov as saying easing sanctions would be possible only if Iran could offer assurances its nuclear program was exclusively for peaceful purposes, as the Islamic republic has maintained.
"There is no certainty that the Iranian nuclear program lacks a military dimension, although there is also no evidence that there is a military dimension," he said.
Russian leaders hope the talks would move into a "bargaining" phase.
"There needs to be a political will to move into that phase," Ryabkov said. "We call on all participants not to lose any more time."