Iran wants the United Nations to condemn last month's assassination of an Iranian nuclear scientist and the wounding of another one.
In a letter circulated at the UN, Iranian UN Ambassador Mohammad Khazaee said the "terrorist attacks" were aimed at disrupting Iran's peaceful nuclear program, but that they would not work.
Iran blames Israel and Western powers for the separate bombings in Tehran on November 29 that killed Majid Shahriar and wounded Fereidoun Abbasi.
The UN suspects Abbasi of links to secret nuclear activities.
Earlier, Western nations on the Security Council accused Iran of using "complex and complicated" methods to trade arms and explosives in violation of U.N. nuclear sanctions.
British Ambassador Mark Lyall Grant suggested a possible tightening of sanctions during council consultations.
U.S. Ambassador Susan Rice said sanctions should remain on Iran until it takes "constructive steps" to prove its nuclear program is for peaceful purposes.
compiled from agency reports