Hezbollah leader Hassan Nasrallah said the United States is "entirely responsible" for the ongoing crisis in Gaza, as he added that they have been at war with Israel since Oct. 8.

"America is entirely responsible for the ongoing war on Gaza and its people, and Israel is simply a tool of execution," Nasrallah said in a televised broadcast. The United States "impedes a ceasefire and the end of the aggression."

He also said that his Lebanon-based movement was already fighting effectively against Israel, as Israel waged war against Hamas in Gaza.

"We have already joined the battle since Oct. 8," he said in his first official remarks since the war between Israel and Hamas began. Before the speech, there had been widespread speculation that Nasrallah would formally declare war on Israel.

"Some might find what is happening on our front to be moderate, but if you look at it objectively, you will find it to be important and very big," he said in a televised address.

The Lebanon front was able to attract a third of the Israeli army to the border with Lebanon, he said.

"All possibilities on our Lebanese front are open and all options are on the table and we can go to them at any time," he threatened.

Israel subsequently launched a heavy air bombardment on the Gaza Strip, allegedly with the aim of destroying the Hamas group but its attacks have largely been targeting civilians, killing at least 9,000 and destroying civilian infrastructure, including hospitals, schools, churches, mosques and more.

Nasrallah assured his supporters that Hezbollah's actions so far would not be the end of its operations, and they had had an impact on Israel's military.

Because of Hezbollah attacks, Israel had been forced to move some of its military forces to focus on its northern border, rather than south toward Gaza, Nasrallah said. Israel had also been forced to evacuate settlements near the border, he pointed out.

Earlier in his speech he called on Arab countries in the region to stop oil deliveries to Israel.