* TSX down 0.1%

* Energy sector the only gainer, Mining stocks fall

* Canadian economic activity contracts in March

(Updates prices, details throughout and analyst comments)

April 7 (Reuters) - Canada's main stock index slipped on

Tuesday as investors monitored the situation in the Middle East,

after Iran showed no signs of relenting to U.S. President Donald

Trump's ultimatum to reopen the Strait of Hormuz.

At 10:55 a.m. ET, the S&P/TSX Composite Index was down

0.1% at 33,149.58 points.

As Trump's deadline approached, the U.S. intensified strikes

on Iran, targeting Kharg Island, home to Tehran's main oil

export terminal.

Trump has given Iran until 8 p.m. ET - 3:30 a.m. in Tehran -

to end its blockade of Gulf oilor face massive destruction of

its infrastructure.

"If the U.S. were to go into Iran and do what they say they're

going to do, the markets will probably react negatively

initially, but then they will likely respond positively thinking

this is closer to an end," said Allan Small, senior investment

advisor at Allan Small Financial Group with iA Private Wealth.

"Being in this state is not good for the markets, we are in

limbo".

Escalating Middle East tensions pushed eight of the ten major

sectors on the TSX into negative territory, with energy and

utilities among the only sectors in green as oil prices extended

gains.

U.S. West Texas Intermediate crude futures surged

above $115 a barrel, while Brent crude futures hovered

near $110, pushing the energy subindex up nearly 2%.

The healthcare sector led losses on the benchmark

index with a 1.8% decline, while consumer discretionary stocks

slipped more than 1%.

The gold sub-index and the materials sector

, which includes stocks of metal miners, dropped 0.4%

as silver fell 3%.

Meanwhile, heavyweight financials were down

0.1%.

On the economic front, data showed Canadian economic activity

contracted in March for the first time in four months as

inflation pressures increased.

Among individual stocks, International Petroleum ( IPCFF )

climbed 5.2% after BMO Capital Markets upgraded it to

"outperform" from "market perform".