For four months, European Union foreign policy chief Catherine Ashton and Iranian negotiator Saeed Jalili traded letters trying to pin down a time and place for Iran to meet with a group of powerful countries concerned about its nuclear program. Late last week, they appeared to have settled on a start date: Dec. 5. But they have yet to agree on a venue, a length for the talks or the subject. Iran says it is willing to talk about everything but its uranium enrichment program. The other countries - the United States, Britain, France, Russia, China and Germany - want to talk mostly about the nuclear program. The difficulty in restarting the talks, which have been on hold for more than a year, doesn't bode well, analysts and diplomats say. The latest round of U.N. Security Council sanctions, which by all accounts have been more crippling than anticipated, was intended to force Tehran to begin negotiating seriously about its nuclear program. But Iranian officials, insisting that the program is for peaceful energy purposes, have given little indication they are interested in negotiating. U.S. officials say Iran's well-documented problems with its uranium enrichment program this year have greatly reduced concerns that Iran is on the brink of producing a nuclear weapon, giving extra time to strike a deal. Iran is enriching uranium with a Pakistani version of a half-century-old Dutch design, and 'the Iranians now have discovered that it's a very poor machine,' a senior administration official said, speaking on the condition of anonymity because of the sensitivity of the issue. 'It's prone to breaking down. They've had hundreds and hundreds and hundreds of these things break down.' The enrichment program apparently plateaued at just under 4,000 active centrifuges, he added. 'They could install a lot more if they wanted to, but they've decided that this machine is a loser, so that's why they stopped,' he said, adding that the Iranians appear to have had little success with a more advanced design. Yet the rise of a Republican majority in the House of Representatives could bring new political pressure to bear on the administration, forcing it to harden its stance on Iran and making it more difficult to strike a deal. In the past week, senior GOP figures have been pushing tougher steps. Ilena Ros- Lehtinen, the incoming chairwoman of the House Foreign Affairs Committee, told Reuters that 'if the country with whom we are negotiating with and playing diplomatic niceties with gets the feeling that they can string us along and have no actions take place, I think that's to the detriment of the United States.' She warned against conveying a 'sense of weakness and a lack of resolve.' Although the Obama administration has publicly stressed its interest in negotiations, some administration officials and advisers say they think the president would use military force to set back Iran's nuclear program if it appeared it was on the verge of having weapons capability. Some analysts say they think the tough talk reduces chances of a successful negotiation. 'The stick side has been emphasized so much that it is hard for Iran to hear anything positive,' said Paul Pillar, national intelligence officer for Near East and South Asia from 2000 to 2005, who teaches at Georgetown University. He said military action would be 'an enormous blunder with huge consequences for the United States.' The coming talks will also be complicated by a failed agreement concerning a medical research reactor in Tehran, the centerpiece of the talks last year. At the time, the deal looked like creative diplomacy. Iranian negotiators had agreed in principle to transfer more than 2,600 pounds of low-enriched uranium out of the country so that Russia and France could convert it into the specialized fuel cells for the reactor. The United States would help improve safety at the reactor, which makes medical isotopes for cancer patients. But the deal fell apart as Iranian officials backed away, suggesting that U.S. crowing about its achievement had hurt Iranian pride. Iran renegotiated the deal with Turkey and Brazil, but that pact was rejected by the other powers. Now Iran has indicated that the only part of its nuclear program it is willing to discuss is the research reactor instead of the centrifuge facility at Natanz, which is the source of international concern. Moreover, Iran has begun enriching some uranium to 19.75 percent, bringing it a step closer to weapons-grade, because that is the level needed for the medical isotope facility. 