A truck has collided with a bus in southern Bolivia, killing at least 31 people, according to police – just two days after a deadly crash claimed at least 37 lives.

Officers said the bus rolled some 500m (1,640ft) down a ravine after the collision on Monday, which took place on the highway between Oruro, in the Bolivian Altiplano, and the highland mining city of Potosi.

The driver of the truck has been arrested, while the cause of the accident is under investigation.

Police spokesperson Limbert Choque said men and women were among the dead, and 22 people suffered injuries.

Bolivia’s President, Luis Arce, expressed condolences for the victims on social media: “This unfortunate event must be investigated to establish responsibilities,” he said in a post on Facebook.

“We send our most sincere condolences to the bereaved families, wishing them the necessary strength to face these difficult times.”

On Saturday morning, a crash between two buses killed more than three dozen people in the same region.

It happened between Colchani and the city of Uyuni, a major tourist attraction and the world’s largest salt flat.

Coincidentally, one of the buses was heading to Oruro, where one of the most important carnival celebrations in Latin America is currently taking place.

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More than 30 people were also killed after a bus crash on 17 February.

In that crash, police said the driver appeared to have lost control of the vehicle, causing it to drop more than 800m (2,600ft) off a precipice in the southwestern area of Yocalla.

Bolivia’s mountainous, undermaintained and poorly supervised roads are some of the deadliest in the world, claiming an average 1,400 fatalities every year.

The Pope has had two episodes of “acute respiratory failure”, the Vatican has said.

The 88-year-old has been in hospital since 14 February with a severe respiratory infection that triggered other complications.

The Vatican said the respiratory failures were caused by “significant accumulation” of mucus in his lungs and a “bronchospasm”, akin to an asthma attack.

Doctors were then required to perform two bronchoscopies – a test which sees medics use a long, thin, telescope with a light to look into the lungs – to evaluate the Pope’s air passages, the statement said.

“In the afternoon, non-invasive mechanical ventilation was resumed,” the Vatican continued. “The Holy Father has always remained vigilant, oriented and collaborative. The prognosis remains reserved.”

Vatican sources said the situation had been calm this morning, before becoming worse this afternoon.

The respiratory issues the Pope suffered today are due to an ongoing infection rather than a new one but he is not out of danger, they added.

Asked if the Pope is in good spirits, they gave no answer. When asked if the Vatican’s apartment is getting ready to welcome Francis back, the source said it was too premature to discuss this.

His clinical picture remains complex, they said.

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Earlier on Monday, Pope Francis issued a written message after Vatican officials begged him to let his voice be heard following more than two weeks out of public view.

He thanked his doctors for their care and well-wishers for their prayers, before praying for peace in Ukraine and elsewhere.

“From here, war appears even more absurd,” he wrote.

This has become the longest public absence of his 12-year papacy.

Cardinal Konrad Krajewski presided over the evening rosary prayer in St Peter’s Square on Sunday night.

“Let us pray together with the entire church for the health of the Holy Father Francis,” he said.

Is this the art of the deal or the art of blackmail?

US President Donald Trump’s evening announcement to suspend US military aid to Ukraine came after a weekend through which the question had been: “He wouldn’t actually do that, would he?”

But given his actions over the past 43 days, his rhetoric during the campaign, and his truly transactional negotiating style, the answer was always to be “of course he would”.

It still doesn’t make the move any less dramatic.

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As late as Monday afternoon in the White House, the president claimed he hadn’t discussed the prospect of cutting or pausing American military weapons shipments to Ukraine.

But it was clear his anger and animosity against Volodymyr Zelenskyy after the Friday showdown had been growing.

And just an hour or two later on Monday, after a meeting with his defence and security officials (who are all wholly aligned to his thinking, unlike those in his first administration) he had paused all military aid.

Sources both sides of the Atlantic have told me this is just the latest step in his game of brinkmanship. The White House emphasis on “pause” is important and hints at the moves they expect Zelenskyy now to make.

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President Trump is determined to pressure President Zelenskyy to sign his minerals deal – the first step in his peace plan, which he eventually expects will culminate in Ukraine and Russia around a negotiating table.

He has not explained quite how this happens or what concessions Russian President Vladimir Putin might be asked to make.

In the immediate term, Trump wants to be able to hail the mineral deal as a massive win for the American people as a material return for the money they sent to fund Ukraine’s war, and as the first step to peace in Ukraine.

So much of this is about a domestic trumpeting of his successes as he sees them. He had hoped to do that tonight at his address to a joint session of Congress.

Zelenskyy is resisting not because he doesn’t want peace but because he wants American commitments that it has his back militarily if he is to enter into peace talks with an unreliable Putin which will require him to make concessions.

He wants American security guarantees. All of Europe wants those, while committing to spending more on defence themselves. They are alarmed that Trump won’t give them yet.

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Every European leader was privately appalled by Trump’s treatment of Zelenskyy last Friday. But some European diplomats have told me they think Zelenskyy took the bait when he could have reacted differently.

Zelenskyy’s friends in Europe may now be quietly telling him to shift position, mend the rift with Trump, sign his deal, commit to a ceasefire and then work, with them, to push Trump on the security guarantees.

In Trump’s brutally transactional world where, like it or not, he holds the cards, it may be the only way.