United Nations - Iraqi leader Haider al-Abadi and President Muhammadu Buhari are among more than 100 leaders taking part in a counter-terrorism summit hosted by President Barack Obama at the United Nations next week.
A total of 104 countries are invited to the September 29 summit that will take stock of the US-led campaign to defeat Islamic State jihadists, one year after it was launched.
Iran however has not been invited to the event even though it is playing a major role in the fight against IS in neighboring Iraq, providing military advisers, weapons and trainers to the Iraqi army and Shiite militias.
Some 30 regional organisations and 100 non-governmental groups are invited to the US-hosted summit in a bid by Washington to broaden the approach to counter-terrorism.
"We are trying to address this in a much more global manner," a US official said Tuesday.
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Obama last year vowed to crush IS during his address to the UN General Assembly and called on countries to join the United States in the campaign.
Since then, the jihadists have captured territory in Syria and Iraq and gained a foothold in Libya, Yemen and elsewhere in the Middle East, with alliances as far afield as Nigeria's Boko Haram.
Leaders will discuss combating foreign fighters and countering violent extremism during the meeting held on the sidelines of the UN General Assembly.
Norway's Prime Minister Erna Solberg, whose country was badly shaken by the 2011 massacre of 77 people by right-wing extremist Anders Brieivik, is among the keynote speakers.
Obama last year hosted a Security Council meeting during which a resolution was adopted to curb the flow of foreign fighters joining IS extremists on the battlefields in Iraq and Syria.
But UN monitors report that the number of foreign jihadists has grown to at least 22,000 and there is no sign that the flow is abating.