Lleyton Hewitt and Chris Guccione's doubles victory gave Australia a 2-1 lead over Germany on Saturday in their Davis Cup World Group play-off to earn a key advantage going into the last day.
Australia are bidding to return to the World Group for the first time since 2007 while Germany must win to stay in the top tier after their opening round home defeat to Argentina in February.
After Bernard Tomic and Florian Mayer won Friday's singles to make it 1-1 overnight, Hewitt and Guccione enjoyed a 6-3, 6-2, 2-6, 7-6 (7/4) victory over Benjamin Becker and Philipp Petzschner.
"I always knew it was going to be tough out there, we expected that from the start," said Hewitt.
"When you can look your partner in the eye in the locker room and know you are going to go into battle together, it is something I have really enjoyed with Chris.
"I feel like I can get the best out of him on the doubles court and it is a good belief to have when we are playing out there together."
In Sunday's final two rubbers, Mayer, ranked 25th in the world, plays teenager Tomic, while Hewitt is due to play 21-year-old Cedrik-Marcel Stebe.
The Germans must win both singles matches to be sure of keeping their World Group status and team captain Patrik Kuehnen admitted they are under pressure.
"The cards have been reshuffled, we have to write that defeat off now, but nothing has yet been decided," he said.
"We still have a chance, but we can't be happy with this result."
Guccione enjoyed his seventh straight doubles win for Australia in the Davis Cup and admitted he was surprised by his own record.
"When I play for my country and pull on the green and gold, it seems to bring out the best in me," said the left-hander ranked 567 in the world in singles, but 133 in doubles.
"I enjoy playing with Lleyton and there is nothing better than playing for my country."
Having clinched the first two sets, the Australian duo allowed their German hosts to establish themselves enough to take the third convincingly at Hamburg's clay-court Rothenbaum stadium.
A tight fourth set was only decided by a tie-breaker, but Hewitt, 31, and the 27-year-old Guccione held on to put their side ahead before Sunday's remaining final matches.
"They compliment each other well, but the Germans were coming back at the boys and fighting hard," said Australia team captain Pat Rafter.
"They were showing a good fighting spirit and we are happy it didn't go to a fifth set."
On Friday, Tomic dug deep after losing the first set to seal a 2-6, 6-3, 6-4, 7-6 (7/4) over Stebe before Mayer earned a 7-5, 6-3, 6-2 win over ex-world number one Hewitt.