US television host Savannah Guthrie has expressed gratitude for the millions of people praying for her 84-year-old mother,  Nancy Guthrie, who has been missing for more than three weeks.

In a social media video, Savannah spoke candidly about the family’s fear and longing, saying: “Every hour and minute and second has been agony…most of all, just missing her. We still believe. We still believe in a miracle. We still believe that she can come home.”

She thanked people for lifting her mother up in prayer. “We feel those prayers,” she said. “Please keep praying without ceasing.”

While acknowledging the uncertainty of her mother’s fate, Savannah said her family continues to cling to hope. “We are blowing on the embers of hope,” she said. “She may already be gone. She may have already gone home to the Lord...if this is what is to be, then we will accept it, but we need to know where she is. We need her to come home."

To aid the search, the family is offering a reward of up to $1m (£740,590) for information that could lead to Nancy’s recovery. Savannah also announced a $500,000 (£370,295) donation to the National Center for Missing and Exploited Children to support other families coping with loss.

“Our hope is that the attention given to our mum and our family will extend to all families in need of prayers and support,” she said. “Please be the light in the dark.”

Nancy was last seen on 31st January after being dropped to her Arizona home by relatives following a family dinner. She was reported missing the following day after she didn't show up to church.

The FBI is assisting local authorities in the investigation.