The Trump administration does not have “a lot of room left here to apply pressure” to prevent North Korea from inching closer to a nuclear weapon that could strike anywhere on the United States, a homeland security advisor to the U.S. president said on Tuesday.

As it continues to pursue nuclear weapon capabilities, ruthless North Korean dictator Kim Jong-un has also stepped up cyberattacks.

“President Trump has used just about every lever you can use, short of starving the people of North Korea to death, to change their behavior,” Thomas Bossert, who serves as U.S. President Donald Trump’s homeland security advisor, told reporters at the White House. “And so we don’t have a lot of room left here to apply pressure to change their behavior.”

The pressure campaign “will be intensified as time goes by,” declared U.S. Secretary of State Rex Tillerson, referring to the economic sanctions against North Korea that have piled up under Trump.

On Tuesday, the Trump administration pledged to hold North Korea accountable for a May cyberattack that affected 150 countries.

The Associated Press (AP) reports:

The WannaCry ransomware attack infected hundreds of thousands of computers worldwide and crippled parts of Britain’s National Health Service. It was the highest-profile cyberattack North Korea has been blamed for since the 2014 hack of Sony Pictures after it produced The Interview, a satirical movie imagining a CIA plot to kill leader Kim Jong-un.

It was “a reckless attack, and it was meant to cause havoc and destruction,” said Bossert, referring to the cyberattack.

He told reporters it put British lives at risk.

“Sanctions on North Korea really aren’t going to change its behavior,” James Lewis, a technology and intelligence expert at the Center for Strategic and International Studies, told AP.

He reportedly “proposes not just targeting North Korea’s revenue sources but also its government’s own limited access to the internet.”

North Korea has intensified its cyberattack capabilities in recent years.

“South Korea, which said in 2015 that North Korea had a 6,000-member cyber army, says the North was suspected of hacking a South Korean military data center,” reports AP.

“Last year, the North was also accused of hacking the personal data of more than 10 million users of an online shopping site and dozens of email accounts used by government officials and journalists,” it adds. “It is also suspected of targeting South Korean banks and the operator of the nation’s nuclear power plants.”