There's still some uncertainty regarding how soon copper will shift into deficit. However, positive arguments for the copper price got some support on Friday when a report from Bloomberg stated that five of the world's largest mining companies have all said good things about the red metal over the last month. BHP Billiton (NYSE: BHP,ASX:BHP,LSE:BLT) CEO Andrew Mackenzie sees copper as the exception in an otherwise uninspiring market space, while Jean-Sebastien Jacques of Rio Tinto's (NYSE:RIO,ASX:RIO,LSE:RIO) copper division simply said in an interview, "we love copper." Meanwhile, Antofagasta's (LSE:ANTO) Diego Hernandez continues to be skeptical of a copper surplus, with Glencore (LSE:GLEN) CEO Ivan Glasenberg echoing that sentiment, telling shareholders on May 7 that his company believes copper is moving into deficit. For his part, Freeport-McMoRan (NYSE:FCX) Chief Executive Richard Adkerson has reaffirmed his belief in copper's strong mid- to long-term fundamentals. Overall, it looks like there's a fairly similar message coming from all five miners. That's worth some attention from investors given that the companies certainly haven't seen eye to eye on a number of other issues as of late. For example, Rio Tinto CEO Sam Walsh has held strong to plans to continue growing the company's iron ore exports, while BHP has indicated that it will slow its iron ore expansion program. Deficit timeline uncertain Recently, Rio changed its prediction regarding a copper surplus, saying that a deficit will come sooner than expected. "If you had asked me the question in December last year I would have said the inflection point would be three or four years down the road and today it is likely to be 18-24 months down the road," Jacques told the Financial Times in an interview earlier this month. This week, the company reached an agreement with the government of Mongolia for a $5-billion expansion at its Oyu Tolgoi mine.