( CNN ) -- Iran has stepped up its production of high-grade enriched uranium and has re-landscaped one of its military bases in an apparent effort to hamper a United Nations inquiry into the country 's nuclear program , a U.N. report said Thursday . Iran 's facilities have produced 189.4 kilograms ( 417.6 pounds ) of the enriched uranium , an increase of 43.8 kilograms ( 96.6 pounds ) since the last U.N. analysis in May , the report said . That enriched uranium is produced at declared facilities in Iran that do n't include the military base cited in Thursday 's report . Iran has n't allowed the agency access to the military site , called Parchin , and , in fact , has been conducting `` extensive activities '' at that location `` that will significantly hamper the Agency 's ability to conduct effective verification , '' the U.N. International Atomic Energy Agency said in its report . Iran 's expanding nuclear program . `` Significant ground scraping and landscaping have been undertaken over an extensive area at and around the location , with new dirt roads established , '' the report said . Iran must respond to the agency 's concerns `` without further delay . '' Otherwise , the U.N. body wo n't be able to resolve issues about Iran 's nuclear program and `` the existence of possible military dimensions '' to the program , the report said . Many Western diplomats and nuclear experts believe the Parchin site has been secretly used to test high-explosive nuclear triggers , an essential step toward achieving a weapons capability . Iran denies that Parchin has any role in its nuclear program , which it insists is for peaceful purposes . A meeting in Vienna last week between IAEA officials and an Iranian delegation , which in part was to discuss access to the Parchin site , ended without progress . High stakes nuclear poker game in Iran ? Iran acknowledges that it is increasing its number of centrifuges to enrich uranium . President Mahmoud Ahmadinejad said last month that 11,000 centrifuges were now operational , about 1,000 more than estimated by the IAEA in May . In a letter Wednesday to the agency , Iran said the allegations of nuclear activities at the Parchin site were `` baseless , '' the report said . But the IAEA reasserted its ongoing alarm about Iran in Thursday 's report . `` Since 2002 , the Agency has become increasingly concerned about the possible existence in Iran of undisclosed nuclear related activities involving military related organizations , including activities related to the development of a nuclear payload for a missile , '' the report said . World needs to keep 'maximum pressure ' on Iran , Panetta says . CNN 's Michael Martinez and Tim Lister contributed to this report .
NEW : Iran says allegations of nuclear activities at Parchin military site are `` baseless '' Iran 's facilities have produced 189.4 kilograms of the enriched uranium , the report says . It says Iran has re-landscaped a military base to make U.N. inspection more difficult . U.N. demands immediate response , cites concerns over `` possible military dimensions ''