HANOI, June 17 (Reuters) - Vietnam will stick to its economic growth target of 10% this year, despite a widening trade deficit and other challenges, a deputy finance minister said on Wednesday. The Southeast Asian country's trade deficit is estimated to have hit $15 billion in the first half of this year, Nguyen Duc Chi told a press conference in Hanoi, swinging from a trade surplus of $7.6 billion in the same period last year.