President George W. Bush's UN ambassador acknowledged that a new intelligence report concluding Iran stopped nuclear weapons development in 2003 has created fresh obstacles for him as the administration seeks new international sanctions against Teheran. "The initial indications that I get is that the impact is not positive," Ambassador Zalmay Khalilzad said Friday, referring to his conversations with fellow diplomats at the United Nations since the report was released. The US National Intelligence Estimate, or NIE, released on Monday, that says Teheran suspended its nuclear weapons program four years ago and has shown no sign of resuming it. In his conversations with other ambassadors, "some have raised questions - 'do we really need a resolution now?"' he said in an interview with The Associated Press. "It does complicate it." But in a speech at Stanford Law School, Khalilzad said he believed the administration would win over other members of the UN Security Council who are skeptical of the need for sanctions. "I'm cautiously optimistic that we will get a resolution," he said. "The question is, when, and what kind of substance" it will contain? Yet Secretary of State Condoleezza Rice ran into the same new diplomatic headwind on Friday that Khalilzad described here: She was unable to persuade Russian Foreign Minister Sergey Lavrov on the urgency of fresh sanctions. Khalilzad began to outline his strategy for winning over China and Russia, but stopped himself with a laugh, saying he did not want to telegraph his strategy to his counterparts. "Already my task will be very hard given the NIE," he said. "I'm not going to score another goal against myself." The United States and its allies want Iran to obey a UN Security Council demand that it halt its uranium enrichment program, which they believe could be used for nuclear bombs. The sanctions would be meant to enforce the Security Council demand. Iran insists it is only using the program to generate electricity, but Khalilzad said he would seek to persuade his counterparts that progress Iran is making on atomic technology is not acceptable. "I'm going to make the case that the most important part of getting to a nuclear weapons capability is access to fissile material," the ambassador told the law school audience. "Iran is working on enriching uranium in violation of two Security Council resolutions, and once it has mastered the enrichment technology it can produce material that is usable for a bomb." "Everyone has said we don't want an Iran with a nuclear weapons capability," he said. "Therefore, we need to work together to incentivize Iran to cooperate. Khalilzad criticized Iran broadly as he argued for firm dealings with that country. Iran, he said, has undertaken an "assertive pursuit of regional hegemony" and views "its ideology and theocratic state as models to be exported or imposed on others." He accused Teheran of stockpiling conventional weapons to threaten its neighbors and potentially shipping in the vital Persian Gulf. And, he said, Iran has tried to destabilize Iraq, Lebanon and Afghanistan. The response will not only require UN sanctions but also possibly economic sanctions, he said. And Iran will require "a sustained US military presence in the gulf region," Khalilzad said.