* TSX ends down 0.8% at 34,151.32

* Materials group falls 4% as gold slides

* Bank of Canada leaves interest rates on hold

* Apotex closes 12.5% above its IPO price

(Updates at market close)

By Tharuniyaa Lakshmi and Fergal Smith

TORONTO, June 10 (Reuters) - Canada's main stock index fell

to a three-week low on Wednesday as U.S.-Iran tensions rose,

while the Bank of Canada left interest rates on hold as expected

and Apotex Health clinched the largest initial public offering

for the market in five years.

The Toronto Stock Exchange's S&P/TSX composite index

ended down 260.37 points, or 0.8%, at 34,151.32,

marking its lowest closing level since May 19.

* Major U.S. stock indexes posted steeper declines as

chipmaker shares extended recent losses and tensions rose

between the U.S. and Iran.

* U.S. President Donald Trump said the U.S. would attack

Iran again "very hard" following one of the most significant

exchanges of fire overnight since an April ceasefire. He accused

Tehran of taking too long to negotiate a deal.

* "This sort of sabre-rattling in Iran is not helping," said

Brian Madden, chief investment officer at First Avenue

Investment Counsel.

* The materials group, which includes metal

mining stocks, fell 4%. The price of gold was down 4.4% as

investors worried that the war could lead to higher interest

rates globally to curb inflation.

* The BoC left the door open to interest rate hikes if

increased inflation due to higher energy prices grows more

widespread but also interest rate cuts if the U.S. imposes new

tariffs on Canadian goods.

* "By keeping both cuts and hikes in play the bank is

acknowledging that policymakers are operating with genuine

uncertainty," said Michael Constantino, CEO of Webull Canada.

* Energy helped limit the TSX's decline, rising

1.6%. The price of oil settled 2.1% higher at $90.03 a

barrel.

* Shares of Canadian generic drug manufacturer Apotex

ended 12.5% above their IPO price of C$24. The IPO

generated about C$1.3 billion in gross proceeds, making it the

largest for the TSX since 2021.