Image copyright CBS Image caption The boy cannot survive for much longer, and must urgently see his mother, the family say

The Yemeni mother of a dying toddler in California has been granted a waiver to travel to the US to visit her son, officials say.

Shaima Swileh, who currently lives in Egypt, was prevented initially from entering the US due to the Trump administration's travel ban.

Her son, two-year-old Abdullah Hassan, was born with a brain disease that doctors say he will not survive.

The government had faced mounting public pressure to allow the visit.

The Department of State granted Mrs Swileh permission to enter the US on Tuesday morning, according to the Council on American-Islamic Relations (CAIR), a nonprofit advocacy group representing the family.

Mrs Swileh is expected to arrive in San Francisco on Wednesday evening, local time, CAIR said, and will see her son before he is taken off life support.

"This is the happiest day of my life," Abdullah's father, Ali Hassan, 22, said in a CAIR statement. "This will allow us to mourn with dignity."

Thousands of emails were sent to officials along with tweets and letters from members of Congress in support of the family, according to CAIR.

"We are so relieved that this mother will get to hold and kiss her son one last time," CAIR-Sacramento attorney Saad Sweilem said.

"The public outpouring of support for this family was incredible."

The organisation also rebuked the government for enforcing the travel ban to begin with, saying the toddler "could have been receiving comfort from his mother" for weeks.

The administration, CAIR said, "required a massive public mobilisation to commit an act of humanity".

The state department had declined to comment on this specific case earlier, but said the US makes "every effort to facilitate legitimate travel by international visitors".

What is the US travel ban?

Soon after he took office, US President Donald Trump imposed travel restrictions on mainly majority Muslim countries.

The executive order went through several versions before being upheld by the US Supreme Court this summer.

It bans nationals of Iran, North Korea, Venezuela, Libya, Somalia, Syria and Yemen from entering the US.

Image copyright CBS

What is the family's situation?

Abdullah and his father are US citizens, but Mrs Swileh is a citizen of Yemen.

The family had moved to Cairo, Egypt in order to escape civil war in Yemen when Abdullah was eight-months-old.

Abdullah was diagnosed with hypomyelination - a brain disease affecting his ability to breathe.

About three months ago, Mr Hassan brought his son to California for treatment. When doctors in Oakland informed him Abdullah's condition was terminal, Mrs Swileh applied for a visa to join her husband and son.

The family says they received a rejection letter from the state department, citing the US president's travel ban, and had been fighting for a waiver ever since.