The latest round of talks between Iran and the six world powers in addition to the European Union ( EU) started in Moscow on Monday, with all parties expressing wills to continue the dialogue over the Iranian nuclear issue.

After the first day meeting, Russian Deputy Foreign Minister Sergei Ryabkov said the talks between Iran and the five permanent members of the UN Security Council -- the United States, Britain, France, Russia and China plus Germany, known as P5+1, were concrete.

"The main thing is that the sides have demonstrated their political wills to continue the dialogue," Ryabkov told a press conference after the talks, which, he said, were held in a benevolent and business-like atmosphere.

"Not a minute was wasted," he said, adding the talks would continue on Tuesday.

The Russian diplomat also admitted there were some obstacles in the negotiations.

"The key stumbling block is that the stances of the sides are really complicated and hard to reconcile," Ryabkov said.

Russia expected more rounds of negotiations could be held after the Moscow talks, he said.

"We do hope the talks will continue, although it would be premature to speculate on when or where they will be held, and for what purpose. We hope this will become clear tomorrow," Ryabkov said.

A high-level Iranian representative also said the first day meeting was "constructive" and "serious".

"Two plenary sessions were held today in constructive and serious ways. We discussed proposals by the parties and our positions," Deputy Secretary of Iran's Supreme National Security Council Ali Baqeri said.

"We found points of contact on certain issues," he said, without further specifying.

According to the representative, EU foreign policy chief Catherine Ashton has asked for a pause until Tuesday afternoon to reflect on Iran's proposals.

Meanwhile, Baqeri insisted that Iran has the right to use nuclear energy for peaceful purposes, warning that sanctions or the UN Security Council resolutions against the country would not help the talks.

"The transfer of the Iranian nuclear issue from the International Atomic Energy Agency (IAEA) to the UN Security Council was illegal. We consider the adoption of the resolutions and various sanctions against Iran illegal," he said.

After the first day talks, Ashton's spokesman Michael Mann told reporters that the two-day talks may be prolonged if necessary, admitting the talks were difficult.

However, he stressed the Moscow talks were more substantive than the previous round held in the Iraqi capital city of Baghdad in May.

The outcome of the talks depends on Iran's response to the international mediators' proposals, Mann said, adding that it was likely to see something to be "put on paper" as a result of the Moscow talks.

Mann's comments was in contrast with his remarks before the meeting started. In the morning, Mann told reporters that the EU was not waiting for a breakthrough during the Moscow talks.

The EU wanted Iran to halt its enrichment of uranium to 20 percent purity, "our position remained unchanged," Mann said.

He also stressed that the EU would not revoke its oil embargo against Iran, which will take effect on July 1.

Also on Monday, spokesman of China's Foreign Ministry Liu Weimin said in Beijing that China always advocates that dialogues and negotiation are the only right and effective ways to resolve Iran's nuclear problem.

"We hope all relevant parties will enhance diplomatic efforts, properly deal with differences, so as to push for substantive results in the Moscow talks," Liu said.

He also urged parties concerned to ensure the positive momentum of cooperation, and seek a comprehensive, long-term and proper resolution to the Iranian nuclear issue.

The last two rounds of talks over the issue were held in Turkey 's Istanbul in April and Baghdad in May, with all sides describing the talks as positive and agreeing on further negotiations.

The UN has by now imposed several rounds of sanctions against Tehran for its refusal to halt uranium enrichment, a technology that can be used to produce nuclear fuel or materials for bombs.

The European Union, the United States and some other countries have imposed oil embargo as part of their sanctions to pressure Tehran into resuming talks on the country's nuclear program.

They have also imposed tough banking sanctions aiming at limiting Iran's ability to sell oil, which accounts for 80 percent of its foreign revenues.