WASHINGTON - One of America's longest serving, most experienced and highest-ranking diplomats, Deputy Secretary Bill Burns, who led secret talks with Iran in recent years, is to retire this year, officials said late Friday. President Barack Obama praised Burns for his 32-year career saying he had "relied on him for candid advice and sensitive diplomatic missions. He has been a skilled advisor, consummate diplomat, and inspiration to generations of public servants." Secretary of State John Kerry said Burns, who had agreed to put his retirement on hold when Kerry took up his post in 2013, had had an "enormous impact and influence in untold ways."Burns, who has worked under 10 secretaries of state, was "a diplomat's diplomat, with this terrifically rare mix of strategic vision and operational skill," Kerry said in a statement."