At least 48 Conservative Party members of Britain's Parliament have signed a letter to trigger a no-confidence vote in Prime Minister Theresa May. Graham Brady, leader of the 1922 Committee that oversees Tory leadership contests, says the vote will happen between 6 and 8 p.m. on Wednesday, London time (1-3 p.m. ET). If May gets fewer than 158 votes, or a majority of Conservative MPs, she will be forced to step down and the Tories would vote on a new leader. If she wins, she can't be challenged again for another year.

The leadership challenge is from pro-Brexit Conservatives who are concerned that she is bungling Britain's divorce from the European Union, especially after she pulled her unpopular Brexit plan before a House of Commons vote on Monday. "Normally when a prime minister loses her main policy she resigns, that is the main constitutional convention, they don't just carry on regardless," Tory MP Jacob Rees-Mogg, a former May ally who signed the no-confidence letter, told CNBC on Tuesday. "The prime minister only holds office as long as she maintains the confidence of the House of Commons." Peter Weber

Tibor Nagy, the U.S. assistant secretary of state for Africa, on Friday called for an "independent and credible" investigation into the violence waged by Sudan's paramilitary security forces when they stormed a protest camp in the country's capital, Khartoum, earlier in June, The Associated Press reports.

Sudan's ruling military council, which recently ousted former autocratic President Omar al-Bashir, said it plans to announce the findings of its own investigation on Saturday. Protest organizers say over 100 people were killed by the security forces, while state authorities said the death toll was 61.

Nagy's stance echoes that of the protesters, who are hoping for an internationally-backed probe into the crackdown. The military council, which admitted that it ordered the dispersal of the sit-in, rejected that idea, as did Sudan's chief prosecutor.

Nagy added that he supports the mediation efforts by the African Union and Ethiopia's Prime Minister Abiy Ahmed, but did not say whether Washington would take any measures if the situation worsens. Tim O'Donnell

One might recall President Trump declaring in an April speech that Sen. Elizabeth Warren (D-Mass.), a 2020 presidential candidate, was "finished." Now, though, Trump's re-election campaign team considers Warren a legitimate threat and is reportedly ready to make her a target, Politico reports, based on conversations with multiple Trump advisers.

Trump aides and their allies at the Republican National Committee are reportedly digging up opposition research and deploying camera-wielding trackers in the hopes of halting Warren's momentum. They also reportedly plan to label her a "liberal extremist." Trump's advisers are reportedly concerned by Warren's disciplined style mixed with "populist-infused" speeches and her potential ability to win over suburban female voters.

The change in tune doesn't mean the Trump campaign won't continue to focus its energy on the current frontrunner, former Vice President Joe Biden, as well, Politico reports; but they're just less certain he'll face off against the president in the general election now.

Warren's prospects looked rough out of the gate, but the senator has polled well recently and has even surpassed Sen. Bernie Sanders (I-Vt.), long considered Biden's top challenger, in some of the latest tallies. Tim O'Donnell

It's unlikely to make a difference in outcome, but Sen. Susan Collins (R-Maine) said on Friday she will oppose one of President Trump's federal judicial nominees, anyway, The Washington Post reports.

Collins, who has opposed Trump on various occasions before, specifically cited nominee Matthew Kacsmaryk's "alarming bias against LGBTQ Americans and disregard for Supreme Court precedents," such as Roe v. Wade, as her primary reasons for doing so. Again, it would be a surprise if Collins' opposition makes any difference regarding Kacsmaryk's confirmation, but it is notable because of the senator's decision to vote to confirm Supreme Court Justice Brett Kavanaugh last year, which led her to face intense criticism from liberals, the Post reports. Collins was singled out, in particular, because of her past willingness to split from her own party.

Kacsmaryk currently serves as deputy general counsel to First Liberty Institute, which defends religious freedom issues. He also defended the right of a shop owner to refuse to bake a cake for a gay couple's union in a high-profile case three years ago, the Post reports. LGBTQ and women's rights groups reportedly "vehemently" oppose his nomination. Read more at The Washington Post. Tim O'Donnell

President Trump on Friday told Fox News that "it doesn't matter" if China's President Xi Jinping meets with him at the G-20 summit in Osaka in June. But, Bloomberg reports, Trump is indeed thinking long term when it comes to trade negotiations with China.

Vice President Mike Pence was reportedly set to give a speech on June 4, the anniversary of the Tiananmen Square massacre, criticizing China's human rights record. The president, though, reportedly stepped in before it could happen in an effort to avoid upsetting Beijing before the summit, four people familiar with the planning told Bloomberg. Trump also reportedly postponed sanctions on Chinese surveillance companies that Pence planned to preview in his speech.

Pence's remarks were then tentatively rescheduled for June 24, just a few days before Osaka, but there is now debate within the Trump administration over when Pence should deliver the speech and, perhaps more importantly, how much he should challenge Beijing during it. If Pence ultimately does go ahead with his remarks, experts, such as Robert Daly, the head of the China program at the Wilson Center, say Beijing's officials would watch it very closely, monitoring for signs that the White House is willing to resume trade negotiations. Read more at Bloomberg. Tim O'Donnell

That's one victory for wildlife conservation.

Niassa, one of the largest wildlife preserves on the African continent, situated in a remote region in northern Mozambique, has marked a year without a single elephant found killed by poachers; the last time a killing was reported was May 17 of last year.

Thousands of animals have reportedly been slaughtered in the region in recent years, but the introduction of a rapid intervention police force and more assertive patrolling and response by air has apparently quelled the damage, the New York-based Wildlife Conservation Society, which co-manages the reserve with Mozambique's government and other partners, said.

Experts have called the drop in elephant poaching an extraordinary development. But despite the progress, it reportedly could still take years to rebuild the elephant population in Niassa to its former levels after aggressive poaching cut initial numbers from around 12,000 to 3,600 in 2016.

Still, wildlife experts are excited by the news. "This represents a major success," George Wittemyer, the chair of the scientific board for the Kenya-based organization, Save the Elephants, told The Associated Press. Other nearby reserves, such as Tanzania's Selous Game Reserve, have also seen recent declines in poaching. Read more at The Associated Press. Tim O'Donnell

Iranian President Hassan Rouhani on Saturday affirmed Tehran will continue to cease complying with certain aspects of the 2015 nuclear deal if other signatories do not soon start showing "positive signals." He did not provide many specifics, including what, exactly, those positive signals would be. Other signatories include China, Russia, the United Kingdom, France, and Germany — the U.S. withdrew from the pact last year.

Tehran announced in May it would start enriching uranium again unless other world powers ignored U.S. sanctions within 60 days. The European signatories have said they want to save the nuclear pact, but several European companies have complied with Washington's sanctions after facing financial pressure from the U.S.

"Obviously Iran cannot stick to this agreement unilaterally," Rouhani said at a meeting with Russian, Chinese, and other Asian leaders in Tajikistan.

Rouhani did not mention the recent attacks on two oil tankers in the Gulf of Oman earlier this week, amid speculation that Iran was behind the act. Tehran has denounced any such accusations, calling them "ridiculous" and "dangerous." Tim O'Donnell