The six world powers finalised a draft U.N. atomic agency resolution on Thursday aimed at increasing diplomatic pressure on Iran to address mounting suspicions that it has sought to design an atomic bomb, diplomats said.

The text, to be debated by the U.N. nuclear watchdog's 35-nation board this week, expressed deep and increasing concern about the unresolved issues regarding the Iranian nuclear programme, including those which need to be clarified to exclude the existence of possible military dimensions, according to a copy seen by Reuters.

It was hammered out by the powers involved in efforts to resolve the nuclear dispute with Iran diplomatically: the United States, China, Russia, Britain, France and Germany, meaning adoption by the full board of governors is virtually guaranteed.

Diplomats described it as a compromise text between Western states, which would have preferred tougher language and a possible referral of Iran to the U.N. Security Council, and Russia and China, which were more reluctant.

They said the IAEA governors were expected to debate the proposed resolution on Friday.

It was drafted in response to an IAEA report last week which said Iran appeared to have worked on designing a nuclear weapon and that secret research may be continuing to that end. Iran has dismissed the allegations as fabricated.

The resolution was agreed in principle already on Wednesday evening, but formal approval from Beijing only arrived the following day, allowing the resolution to be officially submitted to the board for discussion.

It stresses that it is essential for Iran and the Agency to intensify their dialogue aiming at the urgent resolution of all outstanding substantive issues ... including access to all relevant information, documentation, sites, material, and personnel in Iran.

The draft also urged Iran once again to comply fully and without delay with its obligations under relevant resolutions of the Security Council, which has demanded that Tehran suspend sensitive uranium enrichment to foster good-faith negotiations.

(Reporting by Fredrik Dahl and Sylvia Westall; Editing by Mark Heinrich)