President Trump's letter to Iran's Supreme Leader Ali Khamenei included a two-month deadline for reaching a new nuclear deal, one U.S. official and two sources briefed on the letter told Axios. Why it matters: It isn't clear whether the two month-clock begins from the time the letter was delivered or from when negotiations start.

Here’s what to know about the tension between countries, Iran’s nuclear program and a letter Donald Trump wrote to Iran’s Supreme Leader.

Trump revealed this week that he was seeking to strike a new deal with the Iranian regime, after withdrawing from an Obama-era agreement in his first term.