The US state department has said Condoleezza Rice, the US secretary of state, will take part in the meeting at the Red Sea resort of Sharm el-Sheikh and was open to direct talks with Iran over Iraq.
Tehran said it would send a delegation led by Manouchehr Mottaki, the foreign minister, "with the aim of helping the Iraqi nation and government".
"I think it's important, it would be a major breakthrough and any reduction in tensions will positively impact the situation in Iraq," Zebari said in an interview without saying what he thought the US and Iran might discuss.
The high-level conference will bring together Iraq's neighbours, including Syria and Turkey, and world powers.
In Tehran, Iranian foreign ministry spokesman Mohammad Ali Hosseini told state television: "We have emphasised that we are ready for any help to strengthen the government and political process in this country [Iraq]."
Ali Larijani, an Iranian official, arrived in Baghdad on Sunday to give Tehran's formal response on attending the meeting in Egypt.
In other developments, a well-known newsreader from Iraqi state television was shot and wounded on Sunday outside her Baghdad home, her network told AFP.
An Iraqi journalist visits her wounded colleague
Amal al-Muderas at a hospital in Baghdad [AFP]
Amal al-Muderas was attacked by unidentified men in the mixed Khadraa district of western Baghdad, security sources said, apparently the latest victim of attacks aimed at state-run Al-Iraqiya television.
In Baghdad, US forces fired an artillery barrage at targets on Sunday while Iraqi rescuers scoured wreckage for the victims of another car bomb that left more than 70 dead in Kerbala a day earlier.
As the sun rose over the capital, a series of massive detonations could be heard from southwestern districts, where Iraqi officials said a US operation was under way in support of the city's joint security plan.
The death toll from Saturday's suicide bombing near a revered shrine in Karbala rose to 71 overnight as scores of victims suffered in hospital wards crowded with 178 wounded.
The US military also said it detained 72 suspects linked to the al-Qaeda network in a series of raids on Sunday in the provinces of Anbar and Salah al-Din, the biggest daily tally of detentions in many weeks.