The United States has blocked demands at the UN security council for an international inquiry into Israel's assault on the Turkish ship carrying aid to Gaza that left nine pro-Palestinian activists dead.

A compromise statement instead calls for an impartial investigation which Washington indicated could be carried out by Israel.

Turkey pressed for the security council to launch an investigation similar to Richard Goldstone's inquiry into last year's fighting in Gaza which prompted protests from Israel when it concluded that Israel and Hamas were probably guilty of war crimes and crimes against humanity.

Ankara wanted the investigation into the raid on the Mavi Marmara to result in the prosecution of officials responsible for the assault and the payment of compensation to the victims.

But in hours of diplomatic wrangling, the US blocked the move and instead forced a statement that called for "a prompt, impartial, credible and transparent investigation conforming to international standards". The US representative at the security council discussions, Alejandro Wolff, indicated that Washington would be satisfied with Israel investigating itself when he called for it to undertake a credible investigation.

The Israeli government is certain to launch its own inquiry in part as a response to domestic criticism that its forces were ill-prepared for the resistance they met on the ship. But any self-inquiry is likely to be met with the same scepticism beyond Israel's borders that met its investigations into last year's Gaza war and its 2006 invasion of Lebanon which criticised aspects of the handling of the operations but did not challenge the underlying claim that they were essential for Israel's security.

The Americans also blocked criticism of Israel for violating international law by assaulting a ship in international waters in the security council statement proposed by Turkey, the Palestinians and Arab nations.

The US instead forced a broader statement that condemned "those acts which resulted in the loss" of life.

However, the security council statement did criticise Israel's siege of Gaza as "not sustainable" and called for a "sustained and regular flow of goods and people to Gaza, as well as unimpeded provision and distribution of humanitarian assistance throughout Gaza".

Turkey's foreign minister, Ahmet Davutoglu, called the raid on the Mavi Marmara "tantamount to banditry and piracy; it is murder conducted by a state".

The French ambassador to the UN, Gerard Araud, said "there was disproportionate use of force and a level of violence which nothing justifies and which we condemn".

Wolff told the security council that the organisers of the flotilla had been irresponsible in trying to deliver aid by sea in the face of the Israeli blockade.