* Asia markets track Wall St rise on earnings optimism
* MSCI ex-Japan up 0.4 pct, Nikkei rises about 1 pct
* Pound pressured as more UK ministers resign
* Oil prices underpinned by supply constraints
By Wayne Cole and Swati Pandey
SYDNEY, July 10 (Reuters) - Asian shares rallied for a third session on Tuesday as hopes for upbeat corporate earnings buoyed Wall Street, while several high-profile resignations from Britain's government kept sterling on the defensive.
MSCI's broadest index of Asia-Pacific shares outside Japan .MIAPJ0000PUS put on 0.4 percent in early trade, adding to a 1.3 percent rise on Monday.
Japan's Nikkei .N225 climbed about 1 percent and South Korea .KS11 0.5 percent, while E-mini futures for the S&P 500 ESc1 firmed 0.2 percent.
Chinese shares were a bit soft with Shanghai blue chips .CSI300 off 0.2 percent after climbing 2.8 percent on Monday for the biggest daily jump since August 2016.
Both the Dow and S&P 500 boasted their biggest gains in more than a month overnight, as bank shares jumped ahead of earnings reports later this week. The S&P banks index .SPXBK posted its sharpest rise since March 26.
The Dow .DJI rose 1.31 percent, while the S&P 500 .SPX gained 0.88 percent and the Nasdaq .IXIC 0.88 percent.
"Many investors are looking ahead to second-quarter earnings season, which begins in earnest Friday...to see how the trade threat is affecting companies," said James McGlew, Perth-based analyst at stockbroking firm Argonaut.
Investors have been on edge recently with the United States and China slapping levies on each other's exports, spurring fears of a global growth slowdown and hurting stocks and commodities.
The story in currency markets was all about political capers in London.
Prime Minister Theresa May's foreign minister and Brexit negotiator quit on Monday in protest at her plans to keep close trade ties with the European Union after Britain leaves the bloc, stirring rebellion in her party's ranks. Secretary Boris Johnson stepped down just hours after Brexit minister David Davis's resignation, emboldening some in her Conservative Party to mull a plot to unseat her.
The uncertainty saw sterling sink as deep as $1.3189 at one stage before bouncing somewhat to $1.3254 GBP=D3 . It was last down 0.1 percent at $1.3248.
Markets still think it likely the Bank of England will hike rates in August, but a full-blown political crisis could change that.
"Heightened political risk at home coupled with Brexit uncertainty may prompt the BOE to repeatedly delay monetary policy normalization in 2018," said Lukman Otunuga, a research analyst at broker FXTM.
"If expectations continue to diminish over the central bank raising UK interest rates, sterling is at risk of experiencing heavy losses down the road."
The pound's pain was a boon for the U.S. dollar which rallied broadly on expectations the Federal Reserve will keep raising its interest rates.
Against a basket of currencies, the dollar bounced to 94.083 .DXY from a low of 93.713. The dollar also edged up to 111.01 yen JPY= , from a trough of 110.30.
The euro EUR= was back at $1.1755, having run into profit-taking at a three-week peak of $1.1790 overnight.
In commodity markets, oil gained on supply disruptions in Canada and Libya and ahead of looming sanctions on Iran. Q/R
U.S. crude CLc1 added 14 cents to $73.99, while Brent LCOc1 rose 23 cents to $78.30 a barrel.
Spot gold XAU= was a fraction firmer at $1,259.02.
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