After President Trump signed an executive order pausing travel to the U.S. for refugees and citizens of seven majority Muslim countries, world leaders are pushing back on the White House directives, with at least one affected nation suggesting it could even retaliate with its own ban on Americans.

Iranian President Hassan Rouhani criticized Mr. Trump Saturday after the executive orders started taking effect, saying that it was “not the time to build walls between nations.”

“They have forgotten that the Berlin Wall collapsed many years ago,” Rouhani said in a speech carried live on Iranian state television. “Even if there are walls between nations, they must be removed.”

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Javad Zarif, Iran’s foreign minister, had harsher words for what he termed on Twitter a “#Muslimban.”

He charged that Mr. Trump’s actions would be considered by history as a “great gift to extremists and their supporters” and said it showed the “baselessness of U.S. claims of friendship with the Iranian people.”

#MuslimBan will be recorded in history as a great gift to extremists and their supporters.1/7 — Javad Zarif (@JZarif) January 28, 2017

Collective discrimination aids terrorist recruitment by deepening fault-lines exploited by extremist demagogues to swell their ranks. 2/7 — Javad Zarif (@JZarif) January 28, 2017

#MuslimBan shows baselessness of U.S. claims of friendship with the Iranian people while only having issues with the Government. 4/7 — Javad Zarif (@JZarif) January 28, 2017

In a statement, Iran’s Ministry of Foreign Affairs called the ban a “blatant insult” to Muslims and Iranians and seemed to threaten its own retaliatory measures against the U.S.

Iran, the statement read, “will engage in a careful assessment of the short and medium-term impact of the decision of the U.S. Government on Iranian nationals” and “will take reciprocal measures in order to safeguard the rights of its citizens.”

Also, the U.S. ambassador to Iraq, Douglas Silliman, has warned the Trump administration to expect major fallout from Iraq after his executive order, according to one U.S. official.

Specifically, according to the official, Silliman cautioned that the Iraqi government is considering banning all American passport holders entry to the country -- a decision that could seriously impact the fight against the Islamic State of Iraq and Syria (ISIS), with the number of American military and contractors working in Iraq traveling in and out of the country. It’s also possible, the ambassador said, that some Americans inside Iraq could be expelled, according to the official.

Other countries -- even western European nations unaffected by the U.S. travel ban -- have weighed in with their own criticism of Mr. Trump’s executive action.

“The reception of refugees fleeing the war, fleeing oppression, is part of our duties,” French Foreign Minister Jean-Marc Ayrault said Saturday at a joint news conference with his German counterpart, Sigmar Gabriel.

Gabriel offered up his own critical views: “The United States is a country where Christian traditions have an important meaning. Loving your neighbor is a major Christian value, and that includes helping people...I think that is what unites us in the West, and I think that is what we want to make clear to the Americans.”

French President Francois Hollande, who spoke with Mr. Trump Saturday in a phone call, warned the U.S. leader against a trend toward an isolationist foreign policy.

“In an unstable and uncertain world, turning inward would be a dead end,” Hollande said he told Mr. Trump in their first phone conversation since the president took office last week.

Some European leaders have been reluctant to comment.

When British Prime Minister Theresa May was asked her thoughts about the executive order, May told reporters only that “the United States is responsible for the United States’ policy on refugees.”

“The United Kingdom is responsible for the United Kingdom’s policy on refugees, and our policy on refugees is to have a number of voluntary schemes to bring Syrian refugees into the country, particularly those who are most vulnerable, but also to provide significant financial contributions to support refugees in countries surrounding Syria,” she said.

May met with Trump Friday in the White House.