Russia is discussing holding joint exercises with North Korea, Defence Minister Sergei Shoigu was quoted as saying on Monday, at a time when the United States has expressed concern about growing military ties between the two countries.

“Why not, these are our neighbours. There’s an old Russian saying: you don’t choose your neighbours and it’s better to live with your neighbours in peace and harmony,” Interfax news agency quoted Shoigu as saying.

When asked about the possibility of joint exercises between the two countries, he said they were “of course” being discussed, it said.

South Korean news agency Yonhap earlier cited South Korea’s intelligence agency as saying Shoigu had proposed to North Korean leader Kim Jong Un that their countries hold a naval exercise, along with China.

Shoigu met Kim in July when he visited North Korea for the 70th anniversary of the end of the Korean War, celebrated in North Korea as “Victory Day“.

The United States said last week it was concerned that arms negotiations between Russia and North Korea were advancing actively, and that Shoigu had tried during his visit to convince Pyongyang to sell artillery ammunition to Russia. Washington has warned before that North Korea could provide weapons to Moscow for use in its war in Ukraine.

South Korea’s National Intelligence Service told the National Assembly that Shoigu appeared to have held a private meeting with Kim during his July trip to agree on broad military expansion, Yonhap reported.

On Saturday, Russia’s ambassador to North Korea, Alexander Matsegora, told TASS news agency that he was not aware of any plans for North Korea to participate in trilateral military drills with China and Russia but that in his opinion it would be “appropriate” in light of U.S.-led exercises in the region.

Russia and North Korea have recently called for closer military ties but North Korea has denied having any “arms dealings” with Russia.

The United States recently imposed sanctions on three entities it accused of being tied to arms deals between North Korea and Russia.

North Korea has conducted six nuclear tests since 2006 and had been testing various missiles over recent years but it rarely holds military exercises with its neighbours.

The United States and its ally, South Korea, hold regular military exercises, which North Korea denounces as preparations for war against it.