A Saudi-led coalition has been carrying out a military campaign in neighboring Yemen since March 2015.
The Saudi kingdom, together with Egypt, Morocco, Jordan and other Middle Eastern and North African countries, initially launched a series of airstrikes on the Houthi-held areas, as well as imposing an air and naval blockade of the country.
From the beginning, the US provided the coalition with intelligence, airborne fuel tankers and bombs.
However, over the last couple of months the situation has escalated, with the involvement of Saudi Arabia's ground troops and private military companies, whilst a bolstered Al-Qaeda has been filling the power vacuum.
The prolonged airstrikes have also killed and wounded thousands of innocent Yemeni civilians, sparking global outrage from human rights groups.
Some in the US have become critical of the decision by the White House to support Saudi Arabia's military adventurism.
The administration's response has been that, while the US is keen on helping the Saudis in its fight against the Houthis, it does not mean it will aid and abet it in all its proxy wars throughout the Middle East.
In a letter to the New York Times, Human Rights Watch's legal and policy director James Ross contested Obama's administration.
"American support for the Saudi-led coalition […] makes the United States a party to the conflict in Yemen under international law. This obligates Washington to investigate coalition airstrikes that may be war crimes for which American forces may be liable," Ross wrote.
"Given the coalition's repeated unlawful attacks in Yemen over the last year, which Human Rights Watch and others have documented, the United States should cease selling bombs to Saudi Arabia or risk complicity in civilian deaths," he added.
The West's stance towards the conflict in Yemen has been controversial. While the EU has condemned the strikes last month, and passed a non-binding vote in favor of a Saudi arms embargo, the UK has kept supplying them with weapons, Sputnik reported.
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