Washington DC. US President Barack Obama has said that it is impractical to expect any agreement between US President Donald Trump and Tehran to be a 'significant improvement' over the 11-year-old comprehensive nuclear deal. In an excerpt of an interview released on Sunday on ABC News' talk show 'This Week', the former president suggested that it would be better to negotiate for an agreement that falls short of Washington's desire to avoid full-scale war. Citing the historic deal reached in 2015, former President Obama said,