By Reuters Staff 2 Min Read FILE PHOTO: A general view of Qatar National Bank's head office building in Doha October 28, 2012. REUTERS/Fadi Al-Assaad DUBAI (Reuters) - Qatar National Bank (QNB), Gulf’s biggest bank by assets, expects its business in Saudi Arabia will pick up only gradually after reviving its Riyadh branch that was dormant for more than three years due to a diplomatic and economic rift. A QNB executive made the comments to analysts on Monday after Riyadh announced a deal on Jan. 5 to end the dispute with Doha that forced Qatari firms to halt business in the kingdom and its airline to reroute flights around Saudi airspace.