Israel-Gaza-Lebanon updates: Iranian president responds to Israel's retaliatory attacks

The World Health Organization announced Wednesday that it has been forced to postpone the third phase of the polio vaccination campaign in Gaza.

The WHO blamed "escalating violence, intense bombardment, mass displacement orders and lack of assured humanitarian pauses across most of northern Gaza."

The third and final round of the vaccination push was due to start on Wednesday, the WHO said, and aimed to vaccinate 119,279 children across northern Gaza.

"The current conditions, including ongoing attacks on civilian infrastructure continue to jeopardize people's safety and movement in northern Gaza, making it impossible for families to safely bring their children for vaccination, and health workers to operate," the organization wrote in a statement published on its website.

-ABC News' Morgan Winsor

Secretary of State Antony Blinken will travel to Qatar and the U.K. after his Wednesday stop in Saudi Arabia, the State Department announced.

Blinken left Israel early Wednesday following meetings with officials including Prime Minister Benjamin Netanyahu on Tuesday.

The visit was the first on a Middle East tour intended to kickstart stalled cease-fire negotiations in Gaza and encourage a diplomatic resolution to the ongoing fighting between the Israel Defense Forces and Iran-backed Hezbollah forces in Lebanon.

Blinken arrived in Saudi Arabia on Wednesday morning ahead of a planned meeting with Saudi Crown Prince and Prime Minister Mohammed bin Salman.

-ABC News' Cindy Smith

Defense Secretary Lloyd Austin told reporters Wednesday that U.S. officials have "not seen evidence" to support Israel's claim of a Hezbollah bunker located under Al-Sahel hospital in southern Beirut.

"We'll continue to collaborate with our Israeli counterparts to gain better fidelity on exactly what they're looking at," Austin added.

Israel claims Hezbollah is using the purported bunker to store hundreds of millions of dollars in cash and gold under the city's southern Dahiya suburb. Hospital officials have denied the allegation.

The area -- known as a Hezbollah stronghold -- has been the focus of its intense airstrikes on the Lebanese capital over the past month.

-ABC News' Chris Boccia

Defense Secretary Lloyd Austin on Wednesday denied reports that one of his senior staffers is under investigation by the FBI in connection with leaked Pentagon documents purportedly relating to Israel's planned retaliatory strike on Iran.

"There's no OSD [Office of the Secretary of Defense] official being named as a part of this investigation," Austin told reporters while in Rome, Italy. "So that is not true at this point."

"I've seen no evidence of that, or any indication that any OSD official will be implicated as part of this."

-ABC News' Chris Boccia