Sales said dismantling Islamic State remains a top national security priority of the US and its partners in a coalition to fight the group. He did not identify the new leader but said the US is looking into his background, including his previous role in the organization and where he came from.
"We know that he is going to be facing a sustained and systematic amount of pressure from us and our partners," he said.
Sales comments come less than a week after the death of IS leader Abu Bakr al-Baghdadi, announced Sunday by US President Donald Trump and confirmed Thursday by the extremist group.
Sales said the US is aware of reports saying Islamic State seeks vengeance for the death of al-Baghdadi, but said the US and its partners are constantly monitoring for Islamic State plots to hit the US domestically or abroad.
Sales made the comments as the department released an annual report on the global terrorism landscape. The report again names Iran as the world's worst state sponsor of terrorism.
It also noted a rise in racially or ethnically motivated terrorism worldwide and said 85 per cent of the terrorism attacks in 2018 occurred in the Middle East, South Asia and Africa south of the Sahara Desert.
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