Islamabad said Sunday's report that the government had agreed to send the parts to the UN was baseless.
"That report is incorrect; that's entirely baseless and speculative," said Pakistan's Foreign Ministry spokesman Jalil Abbas Jilani on Monday.
Diplomats familiar with a UN investigation into Iran's nuclear programme said on Sunday that Islamabad had agreed to send used centrifuge parts to the UN nuclear watchdog to let inspectors compare them with machinery sold to Iran.
The IAEA is investigating contamination by microscopic particles of highly enriched uranium (HEU) found in Iran at a workshop in Tehran, at a pilot enrichment plant at Natanz and at other sites where there were centrifuges.
Blamed on Pakistan
Iran, which argues its nuclear programme is for the peaceful purpose of generating electricity, says the HEU-contaminated equipment came from imported machinery and not from enrichment activities in Iran.
Tehran blamed the traces on contaminated centrifuge components it acquired second-hand from Pakistan.
Islamabad acknowledged for the first time last week that Abdul Qadeer Khan, the father of Pakistan's atomic bomb programme, provided Iran with centrifuges used to produce enriched uranium fuel for nuclear power plants or arms.
But its refusal to allow IAEA experts to take environmental samples inside the country has prevented the watchdog from verifying Iran's explanation.