WASHINGTON -- South Korea and the United States expressed "deep concerns" Thursday over North Korea's definition of the inter-Korean relationship as one between two hostile states and its potential attempt at changing the status quo in the Yellow Sea, Seoul's foreign ministry said.

Their position was announced in a statement after Foreign Minister Cho Tae-yul and US Deputy Secretary of State Kurt Campbell had a breakfast meeting in Washington. The previous day, Cho held his first bilateral in-person talks with Secretary of State Antony Blinken since he took office in January.

"Following the foreign ministerial meeting, (the two sides) expressed deep concerns again over North Korea's definition of the inter-Korean relationship as one between hostile, belligerent states, and over any potential attempt to change the status quo in the Yellow Sea," the statement read.

"They agreed to actively cooperate to be able to deter any provocation by North Korea," it added, noting that Seoul and Washington have been "completely in solidarity" with each other to address North Korean threats and provocations.

The allies' worries over the North's potential attempt to revise the status quo came as Pyongyang has been more vocal in its move to dispute the Northern Limit Line (NLL), a de facto western inter-Korean sea border.

The North has challenged the NLL, arguing that the line was unilaterally drawn by the US-led UN Command after the end of the 1950-53 Korean War.

During the breakfast meeting, Cho asked Campbell to play an "active" role in further developing the bilateral alliance as well as trilateral cooperation with Japan.

Campbell said in turn that he "highly" cherishes the partnerships with South Korea and Japan, and will work to strengthen three-way cooperation through frequent communication with his counterparts in Seoul and Tokyo, according to the ministry.

Cho reiterated his call for the US government to show interest to help ensure that South Korean enterprises expanding their investment in the US can get benefits commensurate with their contributions in America.

In a readout, State Department spokesperson Matthew Miller said that Cho and Campbell discussed concerns over miliary cooperation between the North and Russia.

"They also noted Russia's concerning military cooperation with the DPRK, including Russia's use of DPRK ballistic missiles against Ukraine, which poses a serious threat to regional stability and global nonproliferation," Miller said.

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

The two sides also discussed concerns about China's support to the Russian defense industrial base while they stressed the importance of providing further support to Ukraine, according to Miller.

During the talks on Wednesday, Cho and Blinken also had discussions on North Korea's threats and its military ties with Russia, Miller said in a separate readout.

"The secretary and foreign minister discussed their concerns about the DPRK's increasingly aggressive behavior, repeated violations of UN Security Council resolutions, including its transfer to Russia of ballistic missiles for use against the people of Ukraine, and increased domestic repression," the spokesperson said.

Both sides underscored continued alignment on countering Russia's aggression, Miller said.

In addition, the top diplomats emphasized the "unwavering" strength of the two countries' alliance and reaffirmed the importance of the trilateral relationship with Japan, he said.