Israel's strikes on Iran's nuclear and military sites have pushed the long-simmering rivalry into open warfare, with Tehran retaliating and hitting key Israeli cities. With the US trying to balance diplomacy and deterrence,

Throughout the day on Friday, Israel carried out wave upon wave of strikes on nuclear facilities and missile bases in Iran. The Natanz uranium enrichment site and the nuclear facility in Isfahan have been hit and top military leaders have been assassinated - as have nuclear scientists.

The United States is the main international backer of Israel, Iran's biggest regional foe. It is also a close ally of Sunni Gulf monarchies which for years pursued their own rivalry with the Islamic Republic, seeing it as their main regional threat.

The two sides were scheduled to meet for a sixth round of negotiations on Sunday. Oman, which was set to host the talks, said on Saturday that this round had been canceled.

The United States has pulled some diplomatic staff and military families out of the Middle East, citing unspecified regional security risks.

Iranian officials said on Friday that the United States "shall be held fully accountable" for its support of Israel after the nation took out key Iranian nuclear facilities and killed government leaders in a series of air strikes this week.

National security experts warn that Israel's attack on Iran shows why Chinese land and asset purchases in the U.S. pose a significant threat to American security.