DONALD Trump has called on countries around the world to work together to restore stability and end the humanitarian crisis in Syria, as he accused the country’s president, Bashar al-Assad, of committed “unspeakable crimes” with the backing of Iran.

In an address to Muslim leaders in Saudi Arabia, the US president denounced Iranian aggression and said the “longest-suffering victims” were the Iranian people.

He said they have “endured hardship and despair” under the reckless pursuit of conflict and terror by their leaders.

“Among Iran’s most tragic and destabilising interventions have been in Syria,” Trump said. “Bolstered by Iran, Assad has committed unspeakable crimes, and the United States has taken firm action in response to the use of banned chemical weapons by the Assad regime, launching 59 Tomahawk missiles at the Syrian air base from where that murderous attack originated.

“Responsible nations must work together to end the humanitarian crisis in Syria, eradicate ISIS, and restore stability to the region.

“The Iranian regime’s longest-suffering victims are its own people. Iran has a rich history and culture, but the people of Iran have endured hardship and despair under their leaders’ reckless pursuit of conflict and terror.

“Until the Iranian regime is willing to be a partner for peace, all nations of conscience must work together to isolate Iran, deny it funding for terrorism, and pray for the day when the Iranian people have the just and righteous government they deserve.”

Earlier, in his address to the Arab-Islamic American Summit in Riyadh, Saudi Arabia, Trump said every nation had to share the burden of rooting out terrorism.

“Every nation has an absolute duty to ensure that terrorists find no quarter on its soil,” he said.

Trump said terrorist groups “do nothing to inspire but kill” and all countries must work together to “honestly” confront “the crisis of Islamic extremists and the Islamists and Islamic terror of all kinds”.

He sought to change perceptions of his past Islamophobia, which was evidenced by his attempts to ban people from a number of Muslim-majority countries entering America, and urged leaders from Muslim countries to confront “Islamist extremism”. He stopped short of any reference to “radical Islamic terrorism” – a key term he used frequently to garner support during his election campaign, and which he condemned former president Barack Obama for failing to say.

Trump used his first major foreign policy speech as president to say the fight against terrorism “is not a battle between different faiths, different sects, or different civilisations”.

He said: “This is a battle between those who seek to obliterate human life and those who seek to protect it. Terrorists don’t worship God. They worship death.”

The president added that the US was prepared to stand with those leaders he was addressing in the fight against extremists, adding: “America is prepared to stand with you. But the nations of the Middle East cannot wait for American power to crush this enemy for them.

“We are not here to lecture, we are not here to tell other people how to live ... or how to worship. Instead, we are here to offer partnership, based on shared interests and values.”

Trump urged the leaders to drive extremists “out of your places of worship. Drive them out of your community. Drive them out of your holy land”.

He is hoping to craft a regional security framework that allows the US to reduce its financial and military role by helping traditional allies enhance their capabilities.

The US had sought a coalition of nations in the Middle East with the aim of “stamping out extremism”, and Trump vowed to “strengthen America’s oldest friendships, and to seek new partners in pursuit of peace”.

Trump promised that “America will not seek to impose our way of life on others, but to outstretch our hands in the spirit of cooperation and trust”.

He said: “Will we be indifferent in the presence of evil? Will we protect our citizens from its violent ideology? Will we let its venom spread through our societies? Will we let it destroy the most holy sites on Earth?

“If we do not confront this deadly terror, we know what the future will bring – more suffering and despair.”

King Salman of Saudi Arabia said he was committed to stamping out Daesh and other terrorist organisations, and called Iran “the spearhead of global terrorism”.