(Corrects tax-related charge in first paragraph to $2.6 billion from $2.4 billion)
Jan 18 (Reuters) - American Express Co posted its first quarterly loss in 26 years, due a $2.6 billion charge related to the U.S. tax law overhaul and the credit card issuer also said it would suspend its share buyback program for the first half of 2018.
The company's shares were down more than 2 percent in extended trading on Thursday.
The net loss attributable to common shareholders was $1.20 billion, or $1.41 per share, in the fourth quarter ended Dec. 31, compared with profit of $825 million, or 88 cents per share, a year earlier.
Excluding one-time items, AmEx earned $1.58 per share.
The tax-related charge lowered AmEx's capital ratios and to rebuild that, the company said it would suspend share buybacks for the first half of 2018, but continue paying dividends. (Reporting by Pallavi Dewan in Bengaluru; Editing by Savio D'Souza)