ROME (Reuters) - Events in Iran will cast a shadow over this weeks meeting in Italy of G8 foreign ministers that should have focused on stabilising Afghanistan. With Secretary of State Hillary Clinton absent after hurting her arm, US special representative Richard Holbrooke will take part in the meeting on Afghanistan-Pakistan. Washington will try to rally support among allies for its new strategy of stabilising Afghanistan by focusing more on quelling the Taliban insurgency in Pakistan, said one US official who asked not to be named. On the NATO side of things, weve said were probably not going to get a lot more troops but what we do want is money, trainers, development assistance, a more coordinated and comprehensive effort, said the US official. Iran never answered host Italys invitation to attend the event - something Rome views as a de facto reply of 'no. Iran has lost an opportunity, Italys Foreign Minister Franco Frattini said. Instability in Iran would have the capacity to bleed over into instability in western Afghanistan, said Bruce Riedel, a former CIA officer who led a review of strategy in Afghanistan and Pakistan for US President Barack Obama. The Group of Eight ministers meeting in the northern city of Trieste starts on June 25 before expanding the next day to tackle Afghanistan, more than seven years after US-backed forces toppled the Taliban in the wake of the Sept. 11 attacks.