US Secretary of State Mike Pompeo blamed Iran on Wednesday for threats to American missions in Iraq and said the United States was terminating a treaty of amity with Tehran, which is the target of increasing US sanctions.

"Iran is the origin of the current threat to Americans in Iraq," Pompeo told reporters at the State Department, days after he announced the closing of the US consulate in the Iraqi city of Basra.

The US said on Friday that it will effectively close the consulate in Basra and relocate diplomatic personnel assigned there in wake of threats from Iran and Iran-backed militia, including rocket fire.

On Wednesday, the International Court of Justice (ICJ) handed a victory to Tehran and ordered the US to ensure that sanctions against Iran, due to be tightened next month, do not affect humanitarian aid or civil aviation safety.

Washington responded by pulling out of the treaty, a little-known agreement that was signed long before Iran's 1979 Islamic Revolution that turned the two countries into arch-enemies.

Pompeo said that the US should have pulled out of the treaty decades ago.

"With the decision that was made this morning from the ICJ, this marked a useful point for us to demonstrate the absolute absurdity of the treaty of amity between the US and the Islamic Republic of Iran."

He added: "We're disappointed that the court failed to recognize that it has no jurisdiction to issue any order relating to these sanctions with the US, which is doing its work on Iran to protect its own essential security interests," Pompeo said.

1955 Treaty of Amity

The 1955 Treaty of Amity was signed long before Iran's 1979 Islamic Revolution which ended friendly relations between the countries. 

Tehran had argued that the US sanctions imposed since May by the Trump administration violated the terms of the treaty.

The court ruled on Wednesday that assurances offered by Washington to ensure sanctions do not affect humanitarian conditions were "not adequate."

"The court considers that the US must remove by means of its choosing any impediment arising from the measures announced on May 8 2018," said presiding judge Abdulqawi Yusuf, reading a summary of a ruling by the 15-member panel of justices.

The sanctions may not hurt "exportation to the territory of Iran of goods required for humanitarian needs such as medicines, medical devices and food items and agricultural commodities as well as goods and services required for the safety of civil aviation," he said.

While US sanctions "in principle" exempt food and medical supplies, the court said "it has become difficult if not impossible for Iran, Iranian nationals and companies to engage in international financial transactions" to purchase such goods.

Iran has welcomed the ICJ ruling, saying the decision "proved once again that the Islamic Republic is right and the US sanctions against people and citizens of our country are illegal and cruel."

Iran's Foreign Ministry said, "the United States must comply with its international commitments and lift obstacles to Iranian trade." 

ICJ "abused, politicized and effective" 

Meanwhile, the US national security adviser John Bolton slammed the ICJ as "politicized and ineffective" as he announced that the US pulled out of two international agreements with Iran and Palestine and would review all international agreements that could expose it to binding decisions by the ICJ.

Bolton, citing what he called "Iran's abuse of the ICJ," said the US would also withdraw from the "optional protocol" under the 1961 Vienna Convention of Diplomatic Relations.

"We will commence a review of all international agreements that may still expose the US to purported binding jurisdiction, dispute resolution in the ICJ," Bolton said on Wednesday.

It is the latest withdrawal by Washington from multilateral accords.

In the nearly two years since being elected, US President Donald Trump has withdrawn the US from a nuclear agreement between six powers and Iran, pulled out of a global climate accord, left the UN cultural agency, and threatened NATO military allies that the US would "go its own way" if members did not spend more on defense.