Amid a tense and dramatic confirmation process for President Donald Trump's Cabinet picks, the Senate has confirmed former ExxonMobil CEO Rex Tillerson to be the US Secretary of State.

Mr Tillerson, 64, won approval in a remarkably close vote, 56 to 43, the most contentious vote for the top diplomat in modern US history. Two of the more controversial Secretary of State picks in the past few decades, Henry Kissinger and Condoleezza Rice, made it through confirmation with significantly wider margins than Mr Tillerson – 78 to 7 for former; 85 to 13 for the latter.

The 69th Secretary of State, Mr Tillerson is now charged with promoting President Donald Trump's so-called "America First" policy across the globe, as international leaders express concern worry the President's clamorous approach to foreign policy-via-Twitter.

"Tillerson faces the most difficult task of any Secretary of State in the postwar era in trying to reconcile President Trump’s intention to make a radical break from decades of bipartisan consensus US foreign policy leadership," Ryan C Crocker, a former US ambassador, told the New York Times, "with the reality that, if he succeeds, such a break could lead to global chaos."

His confirmation also comes as roughly 1,000 career diplomats expressed their disapproval of Mr Trump's executive order to temporarily halt travel from seven majority-Muslim countries on the unsubstantiated belief that it will keep the country safe from terrorism.

'This ban … will not achieve its stated aim to protect the American people from terrorist attacks by foreign nationals admitted to the United States,” the dissent memo reads.

Trump and Putin passionately kiss in street mural Show all 14 1 /14 Trump and Putin passionately kiss in street mural Trump and Putin passionately kiss in street mural A lesbian couple kisses in front of mural depicting Russian President Vladimir Putin and Republican presidential candidate Donald Trump, on the walls of a barbecue bar 'Keule Ruke' on May 19, 2016 in Vilnius, Lithuania. Barcroft Media/Getty Trump and Putin passionately kiss in street mural A lesbian couple kisses in front of mural depicting Russian President Vladimir Putin and Republican presidential candidate Donald Trump, on the walls of a barbecue bar 'Keule Ruke' on May 19, 2016 in Vilnius, Lithuania. Barcroft Media/Getty Trump and Putin passionately kiss in street mural VILNIUS, LITHUANIA - NOVEMBER 23: A woman walks past a mural showing U.S. President-elect Donald Trump (R) blowing marijuana smoke into the mouth of Russian President Vladimir Putin on the wall of a bar-b-que restaurant on November 23, 2016 in Vilnius, Lithuania. Many people in the three Baltic nations of Lithuania, Latvia and Estonia are concerned that Russia, because Trump has expressed both admiration for Putin and doubt over defending NATO member states, will be emboldened to intervene militarily in the Baltics. Sean Gallup/Getty Trump and Putin passionately kiss in street mural A woman walks past a mural on a restaurant wall depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. Petras Malukas/AFP/Getty Images Trump and Putin passionately kiss in street mural AP Trump and Putin passionately kiss in street mural A child walks past a graffiti depicting Russian President Vladimir Putin, left, and Republican presidential candidate Donald Trump, on the walls of a bar in the old town in Vilnius, Lithuania, Saturday, May 14, 2016. (AP Photo/Mindaugas Kulbis) AP Trump and Putin passionately kiss in street mural People walk past a mural on a restaurant wall depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. Petras Malukas/AFP/Getty Images Trump and Putin passionately kiss in street mural A man photographs a mural on a restaurant wall depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. Petras Malukas/AFP/Getty Images Trump and Putin passionately kiss in street mural AP Trump and Putin passionately kiss in street mural A young woman walks past a mural showing U.S. President-elect Donald Trump (R) blowing marijuana smoke into the mouth of Russian President Vladimir Putin with the slogan "make everything great again," in reference to Trump's campaign slogan of "Make America Great Again," on the wall of a bar-b-que restaurant on November 23, 2016 in Vilnius, Lithuania. Many people in the three Baltic nations of Lithuania, Latvia and Estonia are concerned that Russia, because Trump has expressed both admiration for Putin and doubt over defending NATO member states, will be emboldened to intervene militarily in the Baltics. Sean Gallup/Getty Trump and Putin passionately kiss in street mural A morning commuter stops to look at a mural on a restaurant wall depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. Petras Malukas/AFP/Getty Images Trump and Putin passionately kiss in street mural Restaurant owner Dominykas Ceckauskas pose next to a mural on the wall of his establishment depicting US Presidential hopeful Donald Trump and Russian President Vladimir Putin greeting each other with a kiss in the Lithuanian capital Vilnius on May 13, 2016. Kestutis Girnius, associate professor of the Institute of International Relations and Political Science in Vilnius university, told AFP -This graffiti expresses the fear of some Lithuanians that Donald Trump is likely to kowtow to Vladimir Putin and be indifferent to Lithuanias security concerns. Trump has notoriously stated that Putin is a strong leader, and that NATO is obsolete and expensive. / AFP / Petras Malukas (Photo credit should read PETRAS MALUKAS/AFP/Getty Images) Petras Malukas/AFP/Getty Images Trump and Putin passionately kiss in street mural A passerby photographs a mural showing U.S. President-elect Donald Trump (R) blowing marijuana smoke into the mouth of Russian President Vladimir Putin on the wall of a bar-b-que restaurant on November 23, 2016 in Vilnius, Lithuania. Many people in the three Baltic nations of Lithuania, Latvia and Estonia are concerned that Russia, because Trump has expressed both admiration for Putin and doubt over defending NATO member states, will be emboldened to intervene militarily in the Baltics. Sean Gallup/Getty Trump and Putin passionately kiss in street mural Getty

It adds: "[The ban] will immediately sour relations with these … countries, as well as much of the Muslim world, which sees the ban as religiously motivated."

But the White House made clear, in response to the dissent memo, that State Department employees who fail to agree with the Trump administration are free to leave their posts.

"Obviously we’re aware of the [dissent memo], but I think that any government official who doesn’t understand the President’s goals in this and exactly what it was," Press Secretary Sean Spicer told reporters, "they should either get with the programme or they can go."

Rex Tillerson refuses to rule out Muslim registry

Still, Tillerson does not quell concerns over national security, especially as it relations to the Trump administration's relationship with Russia.

In the final days of the Obama administration, intelligence officials published a report that concluded the Kremlin backed a campaign to hack the Democratic National Committee to release information that would sway the US election in Mr Trump's favour. While the President has conceded that Russia was the likely culprit behind the cyber attack, he has insisted on fostering a good relationship with President Vladimir Putin.

Additionally, Mr Trump has said he was open to lifting sanctions imposed on Russia in 2014 for their illegal annexation of Ukraine's Crimea peninsula – which could directly benefit ExxonMobil, as Mr Tillerson brokered $500bn (£409bn) energy partnership with the country.

As a result, he was awarded the Order of Friendship from the Russian president, the highest honour a foreign national can receive in the country.

But ExxonMobil had to cease operations in the region in 2014 because of the sanctions – which Mr Tillerson opposed at the time. The head of the oil giant’s Russian operations, Glenn Waller, said the company would return to the project once sanctions had been lifted.