Why did Trump stop the US bombing of Iran?

US Ambassador to the United Nations Mike Walts said on Sunday that President Donald Trump had temporarily halted attacks on Iran to make more room for diplomacy.
Walts added to the Fox News Sunday program, “It opens some room for negotiations, and gives them a limited opportunity.”
Walts did not provide further details about the nature of the talks, but the fighting between Iran and the United States witnessed a relative calm at the beginning of the week. The US Department of Defense (the Pentagon) stopped the bombing after 13 nights that witnessed an escalation of strikes.
A senior official in the Trump administration was asked yesterday, Saturday, about this calm, and he said that the president “has always emphasized his preference for diplomacy, but he made clear to Iran what will happen if it does not sit at the negotiating table seriously.”