WASHINGTON (AP) — The U.S. government on Wednesday imposed financial sanctions on Iran’s foreign minister, Mohammad Javad Zarif, as part of its escalating campaign of pressure against the Islamic Republic.

The highly unusual action of penalizing the top diplomat of another nation comes a month after President Donald Trump signed an executive order placing sanctions on Iran’s supreme leader, Ayatollah Ali Khamenei.

Zarif, in response to the sanctioning, tweeted: “It has no effect on me or my family, as I have no property or interests outside of Iran.”

U.S. officials said Zarif’s travels to New York for official U.N. business will not be inhibited by the new sanctions, in accordance with America’s international obligations.

Zarif met earlier this month with Republican Sen. Rand Paul, a Trump ally, about potentially opening a back channel for restarting nuclear talks between the two countries.