UPDATE 1-India's TCS quarterly profit misses as key clients cut spending

(Adds details on BFSI revenue, operating margin and background)

BENGALURU, Oct 10 (Reuters) - Tata Consultancy Services Ltd reported a lower-than-expected September-quarter profit on Thursday, as India's No. 1 IT services exporter battled sluggish spending by financial clients.

TCS, a part of salt-to-software conglomerate Tata Group, heavily relies on banking clients in the West for revenue like its peers in the $180-billion IT services sector.

However, an escalating trade war between the United States and China, as well as Britain's likely chaotic exit from the European Union have throttled global economic growth and many companies are cutting costs to cope with the slowdown.

TCS' net profit rose 1.8% to 80.42 billion rupees ($1.13 billion) in the three months ended Sept. 30 from a year ago, but missed the average analyst estimate of 82.55 billion rupees, according to Refinitiv data.

Operating margins dropped to 24% from 26.5%.

The company - whose clients include the Netherlands-based ABN Amro Bank, Citigroup UK and Norway's DNB - said revenue in its key banking, financial services and insurance (BFSI) segment rose only 5.3% to 154.27 billion rupees.

Total revenue rose 5.8% to 389.77 billion rupees.

BFSI, the company's biggest earner, contributed to over a third of its revenue in the last financial year.

TCS has reported consistently outperforming results in the flagging global economy, but had said last quarter that it only expected to "sustain double-digit" growth this fiscal year.

Shares of the company ended down 0.77%. ($1 = 71.0850 Indian rupees) (Reporting by Derek Francis in Bengaluru; Editing by Maju Samuel)