Talks between six world powers and Iran on the country's controversial nuclear programme are to resume in Vienna.

Negotiators are expected to begin trying to draft an agreement that will provide a comprehensive solution to the Iranian nuclear issue.

Although meetings have been held since February, correspondents say nothing of substance has yet been agreed.

Both sides hope to build on an interim deal that saw uranium enrichment curbed by Iran in return for sanctions relief.

The accord - which was signed in Geneva in November but only took effect in January - gives them until late July to agree a comprehensive solution, although that deadline can be extended by mutual consent.

The world powers want Iran to scale back its sensitive nuclear activities permanently to ensure that it cannot assemble a nuclear weapon.

But Iran says its nuclear work, which it insists is peaceful, will continue - and wants an end to the sanctions that have crippled its economy ���c����ɳĮ���t�� ������Ц�ݷŴ�N�� ��Ԕ�����������Ҹ� �t�g�����[��Ť��love ��� �Q�����̽�˙C BBΪʲô�ü���������ˮ�� �����Фʤʣ��褷��ȤФʤʣ� ������ů�˵�΢Ц ����qɩ����һЦ.