File Photo: U.S. President Donald Trump leaves the White House in Washington D.C., the United States, on May 8, 2019. (Xinhua/Ting Shen)

WASHINGTON, May 19 (Xinhua) -- U.S. President Donald Trump made a fresh threat against Iran in a tweet Sunday, deviating from his fairly reserved tone days ago.

"If Iran wants to fight, that will be the official end of Iran," Trump tweeted on Sunday afternoon.

The president's new tweet is an escalation of his tough stance on Iran.

When asked by a reporter at the White House on Thursday morning about whether the United States was going to war with Iran, Trump replied "I hope not."

Trump told his acting Defense Secretary Patrick Shanahan on Wednesday that he does not want to go to war with Iran, The New York Times reported on Thursday, citing several anonymous administration officials.

Over recent weeks, Washington has ratcheted up pressure against Tehran with a series of sanctions, designations and military threats, following Washington's year-long campaign against Iran after the U.S. exit from the landmark Iran nuclear deal in May last year.

On Wednesday, the U.S. State Department ordered the non-emergency U.S. employees in both the embassy in Baghdad and the consulate in Erbil to leave Iraq.

Earlier, the U.S. military said the U.S. forces were on high alert in Iraq and Syria over fears of "imminent threats" from Iran-backed forces in the region.

The U.S. measures came amid the tense situation in the region after Trump decided not to re-issue the sanctions waivers for major importers to continue buying Iran's oil when they expired in early May.