Former Wales wing Nigel Walker, however, has resigned as WRU executive director of rugby in response to the team’s decline.
“I’ve had a number of very honest conversations with Warren and I will make no secret of the fact that his position was on the line as we undertook our review,” Tierney said.
“Further than that, like any head coach in any sport, he knows the security of his position is directly related to the performances of the team and that this is a situation that will continue to intensify.
“There is a tough challenge ahead but Warren is more than up for that challenge. We also believe he is equal to it.”
Gatland may be contracted until the 2027 World Cup but his position is set to reviewed again after the Six Nations, with Wales having a tough start to the tournament away to France in Paris on January 31.
“I’ve been pretty honest in terms of welcoming scrutiny and challenge, as well as that I understand the pressures of international rugby with performances and results,” Gatland said.
“I’m pleased to have the support of Abi and the board to take the squad into the Six Nations.
“This group of players has a huge amount of potential and we will be working incredibly hard together to turn around our fortunes on the pitch.
“We know, more than ever, we will be judged on competitiveness, on success and on winning during the 2025 campaign,” the 61-year-old added.
Walker, who has been in post since 2021, said he was standing down as “it’s right I’m judged on performances on the pitch”.