A map shows Iran and other countries in the region including Saudi Arabia.

Although President Biden has tried to revive Iran's tattered nuclear deal, the agreement has steadily unraveled since former President Donald Trump unilaterally withdrew the U.S. from it.

Relations between Washington and Tehran have grown more strained in past months amid U.S. allegations that Iran is supplying Russia with drones for Moscow's war in Ukraine and following Iran's suppression of protests sparked by the death of a young Iranian woman in the custody of security forces last year. (Iran later acknowledged providing drones to Russia.)

A security meeting between U.S. and Gulf officials in the Saudi capital of Riyadh in recent weeks underscored shared concerns they have about the reach of Iran's missiles and drones, and its nuclear program.

Saudi Arabia maintains ties with Russia, but the kingdom's foreign minister recently visited Ukraine's capital of Kyiv and the kingdom pledged $400 million in humanitarian aid there.

The kingdom relies heavily on the U.S. for its defense and weaponry, despite strains in the bilateral relationship over human rights concerns in Saudi Arabia and long-running concerns among Gulf Arab states about the U.S. commitment to their security.

Shared concerns over Iran and a sense among Gulf Arab states that the U.S. is an unreliable security partner pushed countries like the United Arab Emirates and Bahrain to formalize ties with Israel. (Iran and Israel are enemies.) It's unclear how this Chinese-brokered agreement could impact the Biden administration's efforts to persuade Saudi Arabia to establish full ties with Israel.

White House National Security Council spokesperson John Kirby said the U.S. continues to watch China "as they try to gain influence and footholds elsewhere around the world in their own selfish interests." But he said the administration welcomes the deal regardless of the impetus or who sat down at the table, particularly if this agreement can be sustained and lead to an end to the war in Yemen.

The resumption of ties with Iran is a sign that China's role in the region is growing, the U.S. remains an irreplaceable security partner for Gulf Arab states.