Ed Miliband is set to hold his first talks with US counterpart Marco Rubio today - after he jetted off to the Philippines within his first 24 hours of being Foreign Secretary.
He is due to meet with Mr Rubio at the ASEAN (Association of Southeast Asian Nations) summit of foreign ministers on Wednesday.
But the Foreign Secretary could face a tricky task in trying to win over Mr Rubio, a close ally of Donald Trump, following his past criticism of the US President.
The 'Net Zero' agenda of Mr Miliband, which he doggedly pursued in his former role as Energy Secretary, is also anathema to the Trump administration.
And there are concerns in Washington about Mr Miliband's role in blocking the US from using British bases for strikes on Iran.
Meanwhile, Gavin Newsom - the governor of California and one of Mr Trump's fiercest political opponents - has risked complicating matters further by heaping praise on Mr Miliband.
Speaking to The Times, Mr Newsom hailed Mr Miliband as a 'true statesman' and a 'smart choice' as Britain's new Foreign Secretary.
'He understands that the biggest challenges we face - including the climate crisis and affordability - require serious people willing to work across borders and stand up for democratic values,' Mr Newsom added.
In his first bilateral talks with Mr Rubio, Mr Miliband is expected to reiterate his commitment to mending the fraying 'special relationship' between the US and UK.
Transatlantic ties were pushed to crisis point at the outbreak of the Iran war earlier this year.
Former prime minister Keir Starmer initially refused to allow US bombers to strike Iran from British air bases, before later altering his stance to allow their use for 'defensive' operations after Tehran launched missiles and rockets across the Middle East.
Mr Miliband was reported at the time to have been instrumental in leading Cabinet opposition to the use of British bases by the US.
When Andy Burnham later launched his successful bid to oust Sir Keir, senior officials in Mr Trump's administration were said to have privately warned the new PM that appointing Mr Miliband as his Chancellor would be a 'mistake'.
Top US officials were reported to have told senior Labour figures they were concerned about Mr Miliband's opposition to new oil and gas drilling in the North Sea.
Mr Trump himself has frequently criticised the UK Government in public for its stance on fossil fuels.
There will also be concerns that Mr Miliband's undiplomatic comments about Mr Trump in the past will complicate his job in trying to steady transatlantic ties.
In 2018, Mr Miliband branded the US President a 'racist' and 'misogynist' and claimed he had a 'peculiar relationship with Russia'.
He also used an interview with GQ magazine to condemn Mr Trump's 'very scary authoritarian tendencies' and vow to join protests against him visiting Britain.
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