Tuesday’s top story: Justice Department says ex-White House counsel cannot be compelled to appear before Congress. Plus, every Game of Thrones episode, ranked

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Good morning, I’m Tim Walker with today’s essential stories.

Democrat warns of impeachment if McGahn resists subpoena

Donald Trump has blocked the former White House counsel Don McGahn from appearing before the House judiciary committee to testify about the Mueller report, prompting impeachment threats from at least one Democrat on the panel. McGahn was subpoenaed by the committee to answer questions under oath about several instances in which he apparently stymied Trump’s efforts to obstruct justice. But the Department of Justice provided a legal opinion claiming he could not be forced to give testimony.

Michael Cohen. Trump’s former fixer claimed he misled lawmakers regarding the Trump Tower Moscow project at the suggestion of another Trump lawyer, Jay Sekulow, according to newly released transcripts of Cohen’s closed-door testimony to the House intelligence committee.

US rows back Huawei sanctions amid threat of tech cold war

Facebook Twitter Pinterest The Huawei founder and chief executive, Ren Zhengfei, said the US had ‘underestimated’ his firm’s strength. Photograph: Fabrice Coffrini/AFP/Getty Images

Asian markets rallied on Tuesday morning as Washington relaxed some of its sanctions on Huawei, permitting US companies to keep doing business with the Chinese tech giant for a further 90 days before its blacklisting kicks in, to allow for software updates to Huawei handsets and the maintenance of existing networks. The decision came after Huawei’s founder, Ren Zhengfei, warned the Trump administration had “underestimated” his firm, adding: “Sooner or later there will be conflict with the US.”

Trade war. One Huawei executive said the ban was a “cynically timed” blow in the US-China trade war, which the Organisation for Economic Co-operation and Development has warned could knock up to 0.7% off global GDP and cause significant damage to the American economy.

Tech titans. The decision by US firms such as Google and Intel to stop doing business with China’s telecoms giant could mark the start of a full-blown tech cold war, writes Martin Farrer.

Iran hits back at Trump’s ‘genocidal taunts’

Facebook Twitter Pinterest The Iranian foreign minister, Mohammad Javad Zarif, invited Trump to ‘try respect’ when dealing with Iran. Photograph: Eugene Hoshiko/AFP/Getty Images

The Iranian foreign minister has returned fire at Donald Trump in a war of words on Twitter, after the US president threatened an “official end” to Iran as tensions rise in the Middle East. Mohammad Javad Zarif warned against such “genocidal taunts”, tweeting that Trump “hopes to achieve what Alexander, Genghis & other aggressors failed to do. Iranians have stood tall for millennia while aggressors all gone.” He advised Trump instead to “try respect” in his dealings with Iran.

Diplomatic option. The Iranian president, Hassan Rouhani, insisted on Monday he would prefer diplomacy with the US to conflict, but said: “Today’s situation is not suitable for talks.”

Niki Lauda, single-minded hero of Formula One, dies aged 70

Facebook Twitter Pinterest Lauda celebrates a win over rival James Hunt at the 1975 French Grand Prix. Photograph: Lat Photographic/Rex/Shutterstock

Niki Lauda, the three-time Formula One world champion, has died aged 70. The Austrian won his first title in 1975 but suffered a horrific accident at the German Grand Prix the following year, which left him injured and badly burned. Nevertheless, Lauda returned to claim a second championship with Ferrari in 1977, and one more with McLaren in 1984. He went on to senior roles in F1 management, including most recently at Mercedes, where he helped to recruit Lewis Hamilton.

Hunt rivalry. Lauda’s rivalry with the British driver James Hunt was portrayed as a clash of personalities. But Richard Williams says the two men shared a rebellious streak – and a single-minded ambition.

Crib sheet

Millions in Libya were left without running water after supplies to Tripoli and surrounding cities were cut off by an armed group claiming loyalty to Khalifa Haftar, whose Libyan National Army dominates the east and south of the country. The water supply was later restored.

Google has changed its advertising policy to prevent misleading ads by anti-abortion groups , introducing a new rule requiring abortion-related organisations to identify themselves as either providing or not providing abortions.

Three handwritten wills have been found at Aretha Franklin ’s home in Detroit, months after the singer’s death. The most recent, dated 2014, appears to leave her assets to family members and was found under cushions in the living room.

A 49-year-old Nepalese Sherpa who goes by his first name, Kami, has reached the summit of Everest for a record 24th time after his second ascent in a week. He says he intends to climb the world’s highest mountain once more before retiring.

Must-reads

Facebook Twitter Pinterest Trouble in the ranks? Game of Thrones’ final episode aired to mixed reviews on Sunday. Photograph: AP

Game of Thrones: which episode should wear the crown?

Whatever you made of the finale of Game of Thrones, the show at its peak was the most spectacular, sweeping TV drama ever broadcast. The Guardian’s recapper Sarah Hughes ranks all 73 episodes, from Winter is Coming to The Iron Throne.

World’s biggest investor drags its feet on climate crisis

When Blackrock announced it would no longer invest in companies that failed to comply with the Paris climate agreement, the statement turned out to be a hoax. But now the world’s biggest investor, which controls $6.5tn in assets, is being urged to use its influence over the planet’s worst polluters, as Jasper Jolly reports.

How Nigel Farage’s Brexit party copied Italy’s populists

Nigel Farage’s new Brexit party has gone from a standing start to a commanding lead in the UK’s European election polls in just a few weeks. Darren Loucaides explains how Farage closely modelled his digital strategy on that of Italy’s populist Five Star Movement.

‘I love my partner more since his affair’

Staying together after one half of a couple has an affair may seem impossible, but for some Guardian readers, a betrayal, infidelity or deception ultimately made their relationships stronger, healthier and more open. They tell Ammar Kalia how.

Opinion

Trump claims he does not want a war with Iran, but his advisers are raising the stakes in the region – and the risk of a misunderstanding that could lead to conflict – says Peter Westmacott.

As US sanctions continue to damage the Iranian economy, Trump says he is still interested in some kind of grand bargain. Tehran should call me, the president says, perhaps not realising that there would be huge political consequences for anyone who did.

Sport

Almost four months after he underwent surgery to treat a potentially career-ending hip problem, Andy Murray has hinted he may return to Wimbledon this year by playing in the men’s doubles tournament.

The 100mph fastball used to be a rarity in Major League Baseball; now it is a familiar sight. But with golden arms getting more and more common, Ian McMahan asks whether there are limits to the pitching speed a human limb can withstand.

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