Ellen MacArthur's round-the-world record attempt is under threat after her boat Kingfisher 2 stalled off the coast of Brazil on Monday.

The 26-year-old British yachtswoman told BBC Sport that her speed had tumbled to only three knots on the most frustrating day of the voyage, which started 12 days ago.

"The last few hours have been pretty frustrating, probably more frustrating than the rest of the trip put together," MacArthur said.

Everyone on board has crossed oceans before, so it's not like anyone's surprised by the fact that we don't have any wind Ellen MacArthur

"We're basically sitting 350 miles off the Brazilian coast and we have three knots of breeze, which means we are going very, very slowly.

"Sometimes the wind gods are with you and sometimes they're not. We're certainly not having much luck."

Although the forecast for the next couple of days is poor, MacArthur and her crew of 13 are staying positive and focused.

"Everyone on board has crossed oceans before, so it's not like anyone's surprised by the fact that we don't have any wind.

"To go out and race around the world without having times like this is virtually impossible - we're just having our trouble at the beginning.

"Generally we have a good time on board - the guys are awesome and everyone sees the positive side, whatever is going on."

We are sweltering in this incredible heat Ellen MacArthur

For incentive, MacArthur and crew think of the powerful Southern Ocean winds that lie only days away and have the potential to put the record attempt back on course.

"To think of the Southern Ocean as being just days away is incredible.

"And yet it is also frustrating, because we are sweltering in this incredible heat and yet down in the south it will be very cold. The change is going to be massive."

MacArthur is attempting to break the existing Jules Verne round-the-world speed record of 64 days held by Bruno Peyron.

But she may have to go even faster to eclipse the efforts of French skipper Olivier de Kersauson, whose concurrent bid is on record pace.