Greece's debt crisis burst back on to the economic and political agenda today following an extraordinary row at the top of the International Monetary Fund, the body overseeing the Greek government's bailout programme. In simple terms some of the IMF's board members think Greece's debt is "unsustainable", so some of it may need to be written off, whilst others passionately disagree. We'll have reaction from Athens from economist Dr Michael Arghyrou and journalist Katerina Btazak. The pledge to build a wall along the US-Mexican border was a key election promise from President Trump. The BBC's Hugh Sykes reports from the southern US state of Arizona on what businesses and politicians along the border make of the plans. It might sound something of an oxymoron - car companies looking to develop something other than cars - but that's apparently exactly what some of the biggest players in the industry are doing. Mark Garrison from the US business radio programme Marketplace explains all. The BBC's Fergus Nicoll will be joined throughout the programme from New York by Mark Garrison, from New Dehli by Jyoti Malhotra, senior journalist and president of the South Asian Women in Media (SAWM) group, and they'll also be joined from Hong Kong by the BBC's Juliana Liu. PICTURE: A man walks past a graffiti with a EU flag reading in German 'NO' concerning Greece's referendum on the latest offer of a debt deal by the country's EU-IMF creditors, in Athens on June 28, 2015. (Photo: ARIS MESSINIS/AFP/Getty Images)