Ariana Grande has cleared her schedule to be with her ailing grandfather, who is battling cancer.

The 'Problem' singer, who scored her first UK number one with the hit today (06.07.14), flew straight to her native Boca Raton in Florida to be by his side in hospital after performing at Macy's Fourth of July Fireworks Spectacular on Friday (04.07.14), and asked her fans to pray for her 90-year-old Grandpa Grande.

The 21-year-old singer wrote on Twitter on Saturday (05.07.14): ''love u grandps i need u please pull thru (sic)''

She later added: ''thank u for the prayers. my loves u are so powerful... u are in my heart.

''gonna try my best to put my selfishness aside thru this... as much as i want grandps here with me.. i should just want him to be comfortable

''wish u knew how incredible he is.... humble, respectful, hardworking, polite, thoughtful, humorous, generous. an example for all gentlemen (sic)''

After learning of her chart success, Ariana assured her UK fans that she would try to reschedule her trip there soon, suggesting she intends to stay with her family in Florida for a few more days.

She tweeted today: ''thank u so much UK, just heard the news today.... love u more than words

''i'll try my hardest to reschedule my trip out there! can't thank u enough for ur understanding during this time. love u (sic)''