Donald Trump, America's new ruler, had an hour-long phone conversation yesterday with his Saudi counterpart, King Salman, and allegedly they agreed on just about everything. The Saudi government news agency reported:

"The views of the two leaders were identical on the files that were discussed during the call, including the fight against terrorism, extremism, their finance, formulating the appropriate mechanisms for that, and confronting those who seek to undermine security and stability in the region and interfere in the internal affairs of other states."

A White House summary of the phone call was similarly upbeat but included a few more details. Neither account mentioned any discussion of the Trump regime's ban on citizens from seven predominantly Muslim countries travelling to the United States. Saudi Arabia is not affected by the ban at present, though there are indications that it may be at some point in the future.

The immigration-policy goals set out by Trump in his executive order last Friday include a ban on anyone with "hostile attitudes" towards the "founding principles" of the United States. The executive order says:

"The United States should not admit those who engage in acts of bigotry or hatred (including 'honor' killings, other forms of violence against women, or the persecution of those who practice religions different from their own) ... "

If strictly implemented, this would presumably mean refusing entry to any Saudis who actively support the kingdom's social and religious policies.

The White House version of the phone call (though not the Saudi version) also says:

"The President requested and the King agreed to support safe  zones in Syria and Yemen ..."

According to one rightwing American website (theconservativetreehouse.com), "This is a big, big deal." In language reminiscent of the most obsequious Arab media, it announces: "This is a jaw-dropping exhibition of the scope of President Trump’s strategic leverage."

While there has been much debate about possible safe zones in Syria there has been far less talk of them in Yemen and this may be another Trump plan that hasn't been thought through. Where in Yemen would the "safe zones" be, and in what way would they be safe? Safe from American bombs dropped by the Saudi-led coalition? Safe from the Houthis and their allies? Or safe from al-Qaeda and other jihadists?

In theory there are already safe zones in Yemen. They include hospitals, and they are supposedly protected by international law. 

Last August, however, Médecins Sans Frontières (MSF) was forced to withdraw staff from six hospitals in northern Yemen "in the absence of credible assurances" that the Saudi-led coalition would refrain from bombing medical facilities. MSF's decision came after an airstrike on a MSF-supported hospital in Hajjah province killed 14 people including an MSF staff member. It was the fourth time in 12 months that MSF facilities in Yemen had been hit. 

Establishing and maintaining safe zones of the kind the Trump apparently has in mind is far from easy – as was seen in Bosnia in the 1990s. Safe zones in Iraq after the 1991 war were more effective, but they had to be maintained through no-fly zones policed by the US and Britain.

No-fly zones in Yemen would certainly save a lot of lives but imposing them would bring the US into conflict with its Saudi ally.

Safe zones of a different kind were sought by Yemen's Hadi government in 2015, in the early stages of the war. The idea at the time was to create protected areas outside the Houthis' control, thus allowing the exiled government to return from Riyadh and start governing parts of the country again. In that context, "safe zones" simply meant areas under the Saudi-led coalition's control – and they were not particularly safe.

What kind of safe zones Trump has in mind for Yemen is still unclear and, quite possibly, may never become clear.