Trump is turning up the heat on Iran to appease his Israeli and Saudi allies, but how will Russia and Turkey respond?
The Trump administration's sudden escalation of tension against Iran is aimed primarily at reinforcing the anti-Iranian axis led by Israel and Saudi Arabia, Washington's two main allies in the region.
By heightening the rhetoric against Tehran, Trump is laying out a carpet for Benjamin Netanyahu's visit to the White House in 10 days' time.
The symbolic objective of the Israeli prime minister's first meeting with the new US president - and the one which is likely to be highlighted by the US media - may be to verify whether Trump really intends to move the US embassy to Jerusalem, a slap in the face of all Palestinians, both moderate and Islamist, as well as of Washington's European allies.
But the bigger Israeli purpose is to check Trump's line on Israel's settlement strategy and his willingness to use military force against Iran.
On settlements, Trump has already given a huge boost to Netanyahu in advance of the visit by authorising the White House to put out a statement saying that existing Israeli settlements in the West Bank and East Jerusalem are "no impediment to peace".
Although the statement also said further settlement expansion "may not be helpful," its first part repudiates the UN Security Resolution which described all settlements as illegal and which the Obama administration had pointedly refused to veto last month.
Netanyahu will want to know just how far Trump is ready to go in using force against Iran, either directly or by giving a green light to Israel to go ahead with air strikes on Iranian nuclear facilities.
Israeli Prime Minister Benjamin Netanyahu addresses the Jewish Federations of North America's 2015 General Assembly on 10 November, 2015 in Washington, DC (AFP)
During the election campaign Trump ostentatiously sided with the US neocons' belligerent approach to Iran's role in the Gulf and its close links with Hezbollah in Lebanon.
After winning, Trump appointed as his Defence Secretary General James Mattis, who was recently revealed to have argued for air strikes on Iran a decade ago.
The hawks in Washington are already gearing up to give the new president authorisation to use force against Iran pre-emptively at any time. A resolution was introduced in the House of Representatives last month giving Trump permission for this.
The consensus among analysts in the US capital seems to be that Trump's sanctions against Iran in response to the latest of many Iranian missile tests do not mean that he is rejecting the 2015 nuclear deal, even though he regularly denounced it on the campaign trail. Nor are the new sanctions particularly hard-hitting. They target similar entities and middle-ranking officials to those which the Obama administration had already sanctioned.
The bigger issue is the use of force and Trump's tweets that Obama was too "kind" to Iran and that the new president will be different and take “nothing off the table”.
The Flynn factor
Significantly, Michael Flynn, Trump's National Security Adviser, explained the new administration’s policy by accusing Iran of "continuing to threaten the United States and our allies".
Flynn is known for breaking with the neo-con world view by favouring a realist and less ideological approach to Russia, but on Iran he is showing that he is fully in line with the anti-Iranian hawks. This will reassure not only Netanyahu but the Saudis too.
They will be delighted to see Flynn's description of the Houthis in Yemen as an Iranian "proxy terrorist group" even though it is clear that the Houthis are territorially-based local Yemeni insurgents who use the same conventional war-fighting methods as the Saudi-supported pro-government forces.
Retired Army Lt. General Michael Flynn arrives for the Presidential Inauguration of Donald Trump at the US Capitol in Washington, DC, on 20 January, 2017 (AFP)
This statement by Flynn is the second Trump concession to Riyadh, coming after the exclusion of Saudi Arabia from the list of countries whose citizens are hit by the notorious US travel ban.
For separate reasons Israel and Saudi Arabia have made a major issue of a perceived threat from Iran.
For Israel, it is designed to divert attention from the major unsolved regional conflict, the Israeli theft of Palestinian land, as well as to roll back Iran's support for Hezbollah, the main group willing to challenge Israeli policies with direct action.
For Saudi Arabia, the struggle with Iran is aimed at promoting a fictitious explanation of a foreign hand behind the grass-roots Arab Spring-inspired indigenous protests in Bahrain and eastern Saudi Arabia.
Talk of alleged long-standing Iranian expansionism blurs the fact that the actual recent Iranian outreach in the last few years has not been in the Gulf but in the northern part of the Arab world, namely Iraq and Syria, where Iranian forces have come in, at the invitation of those countries’ governments, as a reactive defence against jihadis.
The latest cause for Saudi anger with Iran, and it is shared by the Trump administration, is the exclusion of both countries from last month's Astana initiative for peace in Syria. The Saudis were not invited at all, the Americans only at the last minute.
Iran was in the driving seat, alongside Russia and Turkey, a dramatic sign of Iran's acceptance by major foreign powers. The emerging Saudi, Israeli and Trump triangle will try to reverse this.
How will Russia and Turkey respond?
An Iranian-Turkish detente had already begun to develop long before Trump appeared on the scene.
Although Iranian-Turkish trade has declined somewhat in the last two years, it had grown dramatically during the first decade of Recep Tayyip Erdogan’s AK party rule in Turkey.
The fact that Turkey was run by a largely Sunni Islamist party was no bar to good economic exchanges with the Shia Islamists of Iran, especially as both preside over rapidly modernising economies with a large consumer class.
During the period of international sanctions linked to Iran's nuclear programme Turkish entities helped to undermine the blockade.
Most importantly at the political level, Iran's Foreign Minister Mohammed Zarif was one of the first foreign officials to declare support for Erdogan during last summer's coup attempt.
Iran welcomed the fact that Erdogan's Syrian policy was changing and that Turkish opposition to Iran's ally, Bashar al-Assad, was softening. Iran will now be keen to ensure that Erdogan does not go back on this.
Russian Foreign Minister Sergei Lavrov (C) shakes hands with his Turkish counterpart Mevlut Cavusoglu (R) as Iran's Foreign Minister Mohammad Javad Zarif (L) looks on after a news conference in Moscow on 20 December, 2016 (AFP)
In Russia, the new Trump pressure on Iran will produce a mixed reaction. Vladimir Putin still has to hold his first meeting with the new US president, and he will not want to spoil it by letting US belligerence towards Iran stand in the way or criticising it loudly.
The Kremlin’s priorities are Ukraine and Syria. Putin hopes to have US sanctions lifted as part of a return to regular US-Russian diplomatic dialogue on a footing of mutual respect, equal treatment and no unilateral pressure.
On Syria, Putin wants to ascertain whether the US is truly putting the military and political struggle against so-called Islamic State and other jihadis in Syria ahead of the campaign against Assad, inherited from Obama.
At the same time Russia sees benefits in having good contacts with Iran. It was no accident that on the day after Trump imposed his sanctions on Iran an announcement was made that Iran's President Rouhani would make a long-delayed trip to Moscow next month.
Moscow wanted to send a signal that it does not believe in unilaterally imposed big-power boycotts. Iran wanted to show it has plenty of room for diplomatic manoeuvring, however much the US, Israel and Saudi Arabia would like to isolate it.
The best test for whether the US sabre-rattling of the last few days marks a fundamental shift will come not just with the meeting between Trump and Netanyahu, but the encounter between Trump and Putin which is not yet fixed.
Jonathan Steele is a veteran foreign correspondent and author of widely acclaimed studies of international relations. He was the Guardian's bureau chief in Washington in the late 1970s, and its Moscow bureau chief during the collapse of communism. He has written books on Iraq, Afghanistan, Russia, South Africa and Germany, including Defeat: Why America and Britain Lost Iraq (I.B.Tauris 2008) and Ghosts of Afghanistan: the Haunted Battleground (Portobello Books 2011).