WASHINGTON (AFP) - Top US General David Petraeus said Sunday that Taliban resistance to the major US-led offensive in Afghanistan was formidable but a bit disjointed. On Iran, Gen Petraeus said the US is raising the stakes in its bid to halt Irans nuclear programme, putting the issue on a pressure track. The way the operation was conducted leaped over some of them. But there is tough fighting going on without question, Petraeus, the head of US Central Command, told NBC televisions Meet the Press programme. Petraeus warned the Taliban that Operation Mushtarak was just the beginning of a long-term campaign ordered by Obama and set in place by Gen Stanley McChrystal, who leads the 113,000 US and Nato forces fighting the Taliban. This is just the initial operation of what will be a 12 to 18-month campaign as Gen McChrystal and his team mapped it out, Petraeus said. We spent the last year getting the inputs right in Afghanistan, getting the structure and organisations necessary for a comprehensive civil military campaign, putting the best leaders we can find in charge of those. On Iran, Gen Petraeus said, I think that no one at the end of this time can say that the US and the rest of the world have not given Iran every opportunity to resolve the issues diplomatically. That puts us in a solid foundation now to go on what is termed the pressure track. Thats the course on which we are embarked now, he said. He also said that Irans recent actions on its nuclear programme have led US intelligence agencies to update a December 2007 estimation that seemed to downplay the threat posed by Tehrans atomic programme. There is no question that some of the activities have advanced during that time. There is also a new national intelligence estimate being developed by our intelligence community in the United States, he said. Well probably hear more on that from the International Atomic Energy Agency when it meets here in the next week or so. Clearly, its new director expressed concern about the activities. Petraeus noted that UN Security Council nations are also expressing their concern about Tehrans atomic aims.