US President Barack Obama has asked Congress for 3.7 billion dollars in extra funding to tackle an immigration crisis at the southern border. More than 50,000 unaccompanied children, most from Central America, have been caught trying to cross illegally between October and 15th June.The move comes amid a Congressional gridlock over a wide reaching bill to overhaul the immigration system. Mr Obama is set to meet local leaders in Texas over the issue today.But he has been criticised by members of both parties about not visiting the border personally during a primarily political fundraising trip to the southern state, which shares a lengthy border with Mexico.