A former Egyptian diplomat, he has become one of the world's best-known advocates of non-proliferation.
"Dr ElBaradei will be formally re-appointed to a third term Monday," IAEA spokeswoman Melissa Fleming said on Monday in Vienna, the Austrian capital.
ElBaradei was to address the opening session of the IAEA's week-long annual conference, which sets overall goals for the atomic monitoring body.
The conference was being attended by high-level delegations from the IAEA's 138 member states.
The agency's 35-nation board of governors in June unanimously chose ElBaradei to continue as its director-general, after Washington dropped its opposition to him.
Washington had resisted a new term for ElBaradei, IAEA director-general since 1997, saying two-terms was enough for running an international agency, but received no backing from other members of the board.
Diplomats said ElBaradei had provoked Washington's ire for questioning US intelligence that Iraq had weapons of mass destruction under now deposed dictator Saddam Hussein and for not being tough enough on Iran, which Washington accuses of secretly developing nuclear weapons.
"Dr ElBaradei will be formally re-appointed to a third term"
ElBaradei, 63, has said the "jury is still out" on Iran's intentions, even if IAEA inspectors have discovered that Iran hid sensitive atomic work for almost two decades until the agency's inspection of its program began in 2003.
Final, pro-forma approval of the director-general is up to the general conference, which mainly endorses decisions made by the board of governors, the IAEA's executive arm.
Time for diplomacy
ElBaradei told an IAEA board meeting on Saturday that there is still room for diplomacy on Iran, despite the board's adopting a resolution that could lead to the Islamic Republic being taken to the UN Security Council.
The Security Council could impose penalties, including international sanctions, because of Iran's non-compliance with the nuclear Non-Proliferation Treaty (NPT).
While Iran is certain to come up at the general conference, Fleming said the agenda would cover the whole range of non-proliferation issues with which the IAEA deals.
The issue of Israel, which has not signed the NPT, is expected to be a main subject at the conference, where in past years Arab countries have attacked Israel for allegedly possessing nuclear weapons.
A Western diplomat close to the IAEA said Middle Eastern states would use the conference as a forum to vent their frustration over Iran's being attacked for having alleged nuclear capabilities while the IAEA does not act similarly against Israel.
A resolution may be introduced but the Western diplomat said this would then be withdrawn in a "procedural game where Arabic countries raise yet again the question" of why Israel has not signed the NPT, the safeguards agreement verified by the IAEA.
Javad Vaeidi denies IAEA charge
that Iran is not cooperating
North Korea, which expelled IAEA inspectors in December 2002 and then withdrew from the NPT the following month, is also expected to be discussed.
This year there is hope, since North Korea has pledged to abandon nuclear weapons and invite IAEA inspectors back, although no dates for this have been set.
Besides these verification activities, the IAEA carries out cooperation programmes to help people use nuclear technology, such as getting radiation therapy machines to developing countries to make cancer treatments easier.
Another IAEA theme is promoting nuclear safety. As part of this, it has focused since the 11 September 2001 attacks in the US on "helping countries identify their vulnerabilities" in nuclear security, a spokesman said.
This includes protecting against terrorists' getting radioactive materials to use in so-called dirty bombs, conventional bombs laced with radioactive materials.