A sixth round of nuclear talks between the United States and Iran, previously scheduled for Sunday, was canceled amid escalating tensions between Israel and Iran.

Israel and Iran exchange missile attacks for a third day; nuclear sites hit, death tolls rise, airspace shut, U.S. warns Tehran against retaliation.

DUBAI — Israel unleashed airstrikes across Iran for a third day Sunday and threatened even greater force as some Iranian missiles evaded Israeli air defenses to strike buildings in the heart of the country. Planned talks on Iran’s nuclear program, which could provide an offramp, were canceled.

The push to do a deal on the country’s nuclear program could be revived, even after the Israeli strikes scuppered the latest round of talks.

Countries trade strikes as tensions grow over larger Middle East conflict - Iranian missiles struck an apartment building in the Galilee region, killing four people, as the countries exchanged fire

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.

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.