During a joint media session with South Korean President Park Geun-hye, Biden said President Obama's decision "to rebalance to the Pacific basin is not in question."
"The United States never says anything it does not do," Biden said. "As I said in my visits thus far in the region, it has never been a good bet to bet against America. ... And America is going to continue to place its bet on South Korea."
Biden, wrapping up his Asian tour in South Korea, also visited Japan and China, where he spoke with his Chinese hosts Thursday about the U.S. refusal to recognize China's newly created air defense identification zone in the East China Sea, and about the U.S. determination to "remain a Pacific power diplomatically, economically, and militarily."
Park praised Biden's "profound insights" into foreign matters. The vice president served on the Foreign Relations Committee when he was a U.S. senator.
"The Korea-U.S. alliance is the linchpin to stability and security not just on the Korean Peninsula but in northeast Asia," Park said.
Park said the region was "has seen growing volatility and tensions."
Noting the alliance between South Korea and the United States was 60 years old, Park said, "[We] hope to further build on the trust that we have built over the last six decades to further deepen our relationship and to take it forward ... ."
Biden also met with South Korean Prime Minister Chung Hung-won and both praised the 60-year alliance of the two countries.
"And it also shows that we have a very bright future ahead," Chung said.
"I'm optimistic," Biden said. "I am truly optimistic about the possibilities that we have."
Concerns about the Chinese air defense zone include the fact it overlaps the existing zones of South Korea and Japan. The zone also covers a Japanese-controlled island chain in the East China Sea already the subject of a bitter and escalating territorial dispute between Japan and China.
Along with the United States, South Korea and Japan have refused to recognize the Chinese air defense zone. South Korea has indicated it wants to expand its own air zone in response to the Chinese action.