Geneva, Jan 18 (IANS): The six major world powers resumed talks with Iran Sunday over its controversial nuclear programme after the failure to meet a deadline last year for a comprehensive nuclear deal.

The meeting between Iran and the P5 1 group, comprising the permanent members of the UN Security Council (UNSC) -- China, France, Russia, Britain and the US -- and Germany, began Sunday morning, a diplomatic source said without giving further details, according to a Xinhua report.

The negotiations were focused on bilateral engagements between the US and Iran during the past four days, which started with talks between the US Secretary of State John Kerry and his Iranian counterpart Mohammad-Javad Zarif Wednesday.

According to a report in the Iranian state-run IRIB TV, which Xinhua cited, Zarif Saturday expressed optimism about a solution to his country's nuclear issue, despite wide gaps between Tehran and the world powers on the issue.

He said that "serious, accurate and clear discussions" over the disputed nuclear issue have been held, and "we are seriously doing our job and believe that the solution is within reach".

Iran has been a target of UN sanctions owing to its alleged attempts to build nuclear weapons.

The West accuses Iran of developing nuclear weapons under the cover of a civilian nuclear programme, but Iran insists its nuclear programme is only for peaceful purposes.

The two sides agreed in November last year to extend the deadline for striking a deal to seven months till July 1, 2015.

How much nuclear capability Iran can retain, and the steps to lift the sanctions against Tehran imposed by the West are the main sticking points for the ongoing negotiations.