"Those diplomatic efforts will continue until the first bomb drops," Tillerson said on CNN's "State of the Union."
Tillerson's comments came a day before the latest US-South Korea military exercises off the Korean Peninsula, which Pyongyang claims are rehearsals for a US-led invasion
. The US says the drills are defensive in nature.
Tillerson said prioritizing diplomacy to try to curb North Korea's nuclear ambitions is President Donald Trump's preferred avenue. Despite a statement on Twitter that suggested diplomacy won't work, the President wants to avoid violence, Tillerson said.
"The President has also made clear to me that he wants this solved diplomatically," Tillerson said. "He is not seeking to go to war."
Several weeks ago, Tillerson announced from Beijing that he had direct lines of communication with North Korea and was seeking to cool tensions between North Korea and the United States.
Shortly after Tillerson's comments, Trump took to Twitter
to say he thought Tillerson was "wasting his time" trying to negotiate with North Korea.
Tensions have ratcheted up between the two nations as North Korea continues to develop and threaten the use of its nuclear weapons and long-range missiles, and Trump has threatened to "totally destroy"
the isolated nation.
Asked if Trump's tweets undermined his diplomatic efforts, Tillerson said connections between US and Chinese leaders were close and that the Chinese "are not confused in any way" about US policy toward North Korea.
As for Trump's tweets themselves, Tillerson said the President made the statements he did to try to "motivate action."
Drills set to begin
North Korea renewed their threats to launch missiles into the waters around the US territory of Guam on Friday, in advance Monday's US-South Korea drills.
The joint naval drills will last for 10 days in the waters of South Korea, according to a US statement, and feature a US aircraft carrier and two guided-missile destroyers.
On Friday, North Korea state media KCNA said "reckless moves" by the United States would force the rogue state to "take counteractions."
"The US military action hardens our determination that the US should be tamed with fire and lets us take our hand closer to the 'trigger' for taking the toughest countermeasure," the KCNA report quoted Kim Kwang Hak, a researcher at the Institute for American Studies of the North Korean Foreign Ministry, as saying.
The harsh rhetoric continued on Sunday, with a commentary in state newspaper Rodong Sinmun calling President Trump a "war merchant and stranger of peace."
North Korea had previously threatened to fire missiles close to Guam in August
, further inflaming tensions between Pyongyang and the Trump administration.
CORRECTION: This story has been updated to reflect that military exercises are between the US and South Korea.