The Latest: Trump’s travel ban takes effect as tensions escalate over immigration enforcement

President Donald Trump's new ban on travel to the U.S. by citizens from 12 mainly African and Middle Eastern countries took effect Monday amid rising tension over the president's escalating campaign of immigration enforcement.

Meanwhile, scores of scientists at the National Institutes of Health sent their Trump-appointed leader a letter titled the Bethesda Declaration, a frontal challenge to policies they say undermine the NIH mission, waste public resources and harm people’s health.

Here’s the latest:

Scores of National Institutes of Health scientists have gone public to assail deep program cuts and upheaval at their agency under the Trump administration.

On Monday, more than 90 current employees sent their leader a letter entitled the Bethesda Declaration. It's a frontal challenge to policies it says "undermine the NIH mission, waste our public resources, and harm the health of Americans and people across the globe."

By signing their names, the NIH employees gave up the veil of anonymity common in Washington - and put their jobs at risk. Their declaration was endorsed anonymously by 250 other NIH researchers and staff. Altogether, employees from all 27 NIH institutes and centers registered their dismay with the agency's direction.

Trump is not backing off his battle with Elon Musk, saying Saturday that he has no desire to repair their relationship and warning that his former ally and campaign benefactor could face "serious consequences" if he tries to help Democrats in upcoming elections.

Trump told NBC's Kristen Welker in a phone interview that he has no plans to make up with Musk. Asked specifically if he thought his relationship with the mega-billionaire CEO of Tesla and SpaceX is over, Trump responded, "I would assume so, yeah."

"I'm too busy doing other things," Trump said.

The president also issued a warning amid chatter that Musk could back Democratic lawmakers and candidates in the 2026 midterm elections.

"If he does, he'll have to pay the consequences for that," Trump told NBC, though he declined to share what those consequences would be. Musk's businesses have many lucrative federal contracts.

Johnson took clear sides Sunday in Trump's breakup with mega-billionaire Elon Musk, saying Musk's criticism of the GOP's massive tax and budget policy bill will not derail the measure, and he downplayed Musk's influence over the GOP-controlled Congress.

"I didn't go out to craft a piece of legislation to please the richest man in the world," Johnson said on ABC's "This Week."

Johnson said he has exchanged text messages with Musk since he came out against the GOP bill.

Musk called it an "abomination" that would add to U.S. debts and threaten economic stability. He urged voters to flood Capitol Hill with calls to vote against the measure, which is pending in the Senate after clearing the House. His criticism sparked an angry social media back-and-forth with Trump, who told reporters over the weekend that he has no desire to repair his relationship with Musk.

The speaker was dismissive of Musk's threats to finance opponents - even Democrats - of Republican members who back Trump's bill.

Trump's new ban on travel to the U.S. by citizens from 12 mainly African and Middle Eastern countries took effect Monday amid rising tension over the president's escalating campaign of immigration enforcement.

The new proclamation, which Trump signed last week, applies to citizens of Afghanistan, Myanmar, Chad, the Republic of Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen. It also imposes heightened restrictions on people from Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela who are outside the U.S. and don't hold a valid visa.

The new ban does not revoke visas previously issued to people from countries on the list, according to guidance issued Friday to all U.S. diplomatic missions. However, unless an applicant meets narrow criteria for an exemption to the ban, his or her application will be rejected starting Monday. Travelers with previously issued visas should still be able to enter the U.S. even after the ban takes effect.