US President Joe Biden puts Israel on notice after airstrike kills 7 aid workers

US President Joe Biden has put Israel on notice that support from the US now hinges on it taking action to stop killing civilians in Gaza.

The frank warning came during a tense phone call with Israel's Prime Minister, where Biden unleashed over the airstrike that killed seven aid workers. He also demanded more aid be let into Gaza.

For almost seven months, America has carefully resisted pushing back.

But with an estimated 30,000 killed in Gaza, and as global outrage grows over the deaths of seven international aid workers this week, it seems White House patience is running out - and it's warning Israel to tread carefully.

"If we don't see the changes that we need to see, there will be changes in our own policy," said US Secretary of State Antony Blinken.

President Biden signalled those changes hours earlier directly with Israel. 

Once close friends, the half-hour call between him and Benjamin Netanyahu was described as "tense".

Afterwards, Biden tweeted "strikes on aid workers and the humanitarian situation in Gaza are unacceptable".

He wrote Israel needs to "work toward a ceasefire to bring hostages home".

"He made clear that US policy with respect to Gaza will be determined by Israel's assessment of immediate action on these steps," National Security Council spokesperson John Kirby.

Biden's frustration has been growing, and his language hardening. The President said he was "outraged" just days ago by the killing of those aid workers. They were working for the non-profit World Central Kitchen in Gaza.

Israel says it was an accident, but the group's founder, renowned chef José Andrés, disputes that.

"It was really a direct attack on clearly marked vehicles," he said.

The White House wouldn't pre-empt what policy changes it would make if Israel didn't listen to its warnings.

But other Democrats, who are pressuring the President, are offering some suggestions.

"Frankly I think we're coming to the point where the President is going to have to make a profound decision, and that is are we going to send US munitions, to Israel, that are used in Gaza," said Senator Peter Welch.

The US gives Israel $3 billion worth of military aid, every year.

Today aid vessels carrying food could be seen returning to the safety of Cyprus.

Gaza has been left abandoned, but it's Israel looking increasingly isolated by the international community.