The news from Gaza of innocent Palestinian civilians, including many women and children, being killed by Israeli fire is heartbreaking.

The shelling on Wednesday of a United Nations school serving as a shelter caused the deaths of some 20 people and injured more than 100. An initial UN assessment concluded that Israel was responsible for shelling the facility where 3,300 people were seeking refuge. UN Secretary General Ban Ki-moon has called the attack "outrageous and unjustifiable" and demanded "accountability and justice".

The United States has for the first time "condemned" the attacks on innocent Palestinian civilians in the neutral UN shelter. But it still did not name Israel. In the past days, top US officials and government spokespersons have expressed "regret", and said they are "concerned" or "seriously concerned" over the deaths of innocent Palestinians.

There have been 1,300 deaths and more than 7,000 injuries on the Palestinian side and close to 60 deaths, mostly soldiers, on the Israeli side. These figures tell who has been using force relentlessly.

Even while expressing their concerns over the deaths of Palestinian civilians, US officials and spokespersons often first emphasize that Israel has the right to self-defense. They seem to suggest that there could be a justification of targeting civilians. But to the rest of the world, targeting and killing innocent civilians should never be justified for whatever reasons.

The bias of US officials and news media in this Israeli-Palestinian conflict is nothing new. To the US, Israel is an ally and an exceptional ally. It raises a serious question of impartiality when the US tries to mediate a cease-fire or peace process.

We all remember the trouble US Defense Secretary Chuck Hagel ran into last year during his prolonged confirmation hearing when his track record on Israel was called into question. That is probably why when Pentagon Press Secretary John Kirby said on Wednesday that Hagel called for a cease-fire and expressed concern about the rising number of Palestinian civilian deaths as well as the loss of Israeli lives, he also said Hagel reiterated US support for Israel's security and its right to self-defense.

The same is true for US Secretary of State John Kerry. Despite his busy shuttle diplomacy in the Middle East, which should be lauded, he has to plead his allegiance to Israel before even voicing his concern over the deaths of Palestinian civilians. "I spent 29 years in the Senate and have a 100 percent voting record in favor of Israel," he said on television on Tuesday.

If so many civilians had been killed by a non-US ally, US officials and news media would have been quick to condemn those responsible. But even as the UN condemned Israel over the Wednesday attack based on an initial assessment, US officials and government spokespersons all said they needed further investigation, in sharp contrast to the times when the US has jumped to conclusions, such as in the case of Malaysia Airlines Flight MH17 which crashed on July 17 over Ukraine.

Commentating on the Wednesday morning shelling of the UN shelter, some US officials and TV commentators questioned whether Hamas had stocked missiles and other weapons in the UN shelter, as if the crime of shelling and killing civilians could be pardoned or alleviated if that was indeed true.

As the only superpower in the world, the US could play a major role in mediating an end to the conflict. But that will not be possible until it is willing to adopt an impartial stance. Something that holds true for the US' endeavors in other parts of the world.

The author, based in Washington, is deputy editor of China Daily USA. E-mail: chenweihua@chinadailyussa.com