Tehran has asked Qatar, Saudi Arabia and Oman to press US President Donald Trump to use his influence on Israel to agree to an immediate ceasefire with Iran in return for Tehran's flexibility in nuclear negotiations, two Iranian and three regional sources told Reuters on Monday.

Gulf leaders and their top diplomats worked the phones all weekend, speaking to each other, to Tehran, Washington and beyond in an effort to avoid a widening of the conflict as longstanding enemies Israel and Iran intensified their attacks in their biggest ever confrontation.

Iran is willing to be flexible in the nuclear talks if a ceasefire is reached, one of the Iranian sources said.

The Gulf States are deeply concerned that the conflict will spin out of control, a Gulf source close to government officials told Reuters.

Qatar, Oman and Saudi Arabia have all appealed to Washington to press Israel to agree to a ceasefire and to resume talks with Tehran towards a nuclear deal, the Gulf source said.