Senators from both parties vented frustration Tuesday over U.S. policy on North Korea that the Republican chairman of the foreign relations committee called an “abject failure.”

Republican Sen. Bob Corker of Tennessee told a hearing that North Korea’s nuclear and ballistic missile programs continue to advance and its people are suffering at the hands of the regime of leader Kim Jong Un.

Corker said there’s no “silver bullet” but he wants to work with Republicans and Democrats in Congress to address the North Korean threat.

Sen. Ben Cardin from Maryland, the committee’s top-ranking Democrat, said he doubted whether any country treated its people worse than North Korea, and despite growing world pressure on its human rights record, “it continues to do that.”

“I’m looking for new ideas,” Cardin said.

State Department officials testifying Tuesday didn’t offer any.

Sung Kim, the top envoy on North Korean, said he shared lawmakers’ frustrations over the lack of progress. “We don’t have the option of giving up,” the envoy said.

He said the U.S. will use a combination of deterrence, diplomacy, and pressure to make clear that North Korea will not achieve security or prosperity while it pursues nuclear weapons and abuses its own people.

“It’s persistence more than new ideas that are going to bring about change,” said Robert King, the U.S. envoy on North Korean human rights.

Last week, President Barack Obama said the U.S. is willing to negotiate with the North, as it has with Iran, but it must be willing to discuss giving up its nuclear ambitions — which Kim shows no interest in doing.

North Korea is believed to have a small but growing nuclear arsenal and is developing a mobile ballistic missile that could potentially reach America. South Korean lawmakers in Seoul said Tuesday that South Korea’s spy service believes North Korea is preparing for its fourth nuclear test since 2006 but not in the immediate future.

(AP)