** Shares of COSCO Shipping Holdings Co Ltd 601919.SS rise more than 2% in Shanghai to 3-week high

** The U.S. and China on Tuesday begin charging port fees on ocean shipping firms, making the high seas a key front in the trade war between the world's two largest economies

** Analysts expect China-owned container carrier COSCO to be most affected, shouldering nearly half of that segment's expected $3.2 billion cost from those fees in 2026

** COSCO unveiled share buyback plans on Tuesday

** COSCO's board has approved a plan to buy back up to 1.5 billion yuan ($210.23 million) worth of its own shares within the next three months

** COSCO says buyback aims to maintain corporate value, safeguard shareholder interest, and bolster investor confidence

** COSCO's Hong Kong-listed affiliates also rise

** Cosco Shipping International (Hong Kong) 0517.HK up more than 1%

** COSCO Shipping Ports Ltd 1199.HK up nearly 1%

($1 = 7.1350 Chinese yuan renminbi)

((samuel.shen@tr.com))