The US told the United Nations on Wednesday that the killing of Iranian commander Qassem Soleimani was in self-defence and vowed to take additional action "as necessary" in the Middle East to protect US personnel and interests.

In a letter to the UN Security Council, US Ambassador Kelly Craft (photo) said the US also stands "ready to engage without preconditions in serious negotiations with Iran, with the goal of preventing further endangerment of international peace and security or escalation by the Iranian regime."

The killing of Soleimani in Baghdad on Friday was justified under Article 51 of the UN Charter, wrote Craft in the letter seen by Reuters.

It read that the US is prepared to take additional actions in the region as necessary to continue to protect U.S. personnel and interests."

Under Article 51, countries are required to "immediately report" to the 15-member Security Council any measures taken in exercising the right of self-defence. 

The US also used Article 51 to justify taking action in Syria against Islamic State militants in 2014.

Soleimani (below) was widely seen as Iran’s second most powerful figure behind Supreme Leader Ayatollah Ali Khamenei, 80.

He was killed leaving Baghdad airport last Friday.

On Monday, mourners packed the streets of Tehran for Soleimani’s funeral, chanting: “Death to America!” - a show of national unity after anti-government protests in November in which many demonstrators were killed.

The crowd, which state media said numbered in the millions, recalled the masses gathered in 1989 for the funeral of the Islamic Republic’s founder, Ayatollah Ruhollah Khomeini.

The killing of Soleimani has prompted fears around the world of a broader regional conflict, as well as calls in the US Congress for legislation to keep President Donald Trump from going to war against Iran. - Reuters