TOKYO, April 13 (Reuters) - Japan's Nikkei share average

slipped 1% on Monday as the collapse of U.S.-Iran peace talks

and reports of a U.S. Navy plan to block the Strait of Hormuz

cast fresh doubts on the durability of an ongoing ceasefire.

The Nikkei was down 1% at 56,357.40, as of midday

break, after posting its steepest weekly gain in more than a

year last week. The broader Topix slid 0.5% in choppy

trading to 3,721.78.

U.S. President Donald Trump said on Sunday the U.S. Navy

would start blocking the Strait of Hormuz, a choke point for 20%

of the world's daily energy supplies that Iran effectively

closed since the war started in late February. The announcement

drove oil prices to jump above $100 a barrel in early trade on

Monday.

"I don't think there are that many investors who expected

everything to be agreed (at the weekend talks) and for

everything to go smoothly," said Shuutaro Yasuda, market analyst

at Tokai Tokyo Intelligence Laboratory.

"That said, it's obviously not good news, so stocks are

falling. But I think the reason we're not seeing a really

extreme risk-off move is exactly that."

Across the Tokyo Stock Exchange's 33 industry sub-indexes,

energy exploration stocks stood out with a 3.2% gain.

In contrast, electric power and gas and air transport

each lost 1.8%.

Market breadth was negative, with 162 stocks falling versus

62 advancing in the Nikkei, led by losses in

semiconductor-related stocks.

Ibiden ( IBIDF ), a chip packaging and electronics firm,

recorded the steepest drop among blue chips, falling 4.3%. Tokyo

Electron, a major semiconductor equipment maker, also weighed

heavily in the index, declining 3.7%.

Still, solid corporate earnings helped limit the decline in

market sentiment, said Hiroshi Namioka, chief strategist and

fund manager at T&D Asset Management.

Yaskawa Electric ( YASKF ), an industrial robots and motion

control systems maker, was among the Nikkei's biggest percentage

gainers, up 5.7%. Ryohin Keikaku ( RYKKF ), operator of MUJI

brand, rose as much as 4.6% before paring gains to 1.3%.

"Although the overall market is paying attention to

earnings, when it comes to sector selection, there's no doubt

that the moves are being driven by expectations of crude oil

prices," Namioka said.