SEOUL:  The United States Wednesday announced new sanctions on North Korea following the sinking of a South Korean warship and said the attack could be the start of more provocations by the communist state.

Secretary of State Hillary Clinton said the sanctions were designed to prevent Pyongyang from funding weapons programmes and spreading weapons of mass destruction.

She told a press conference the measures were not directed at the North Korean people, "who have suffered too long due to the misguided and malign priorities of their government".

"They are directed at the destabilising, illicit and provocative policies pursued by that government."

Clinton and US Defense Secretary Robert Gates are visiting South Korea to show support after the sinking of the ship with the loss of 46 lives.

The US and South Korea, citing findings of a multinational investigation, accuse the North of torpedoing the Cheonan near the disputed Yellow Sea border in March -- a charge it denies.

"There has been some indication over a last number of months, as a succession process gets under way in North Korea, that there might be provocations particularly since the sinking of the Cheonan," Gates said.

"So I think it is something that we have to look at very closely, we have to keep in mind and be very vigilant."

Ailing leader Kim Jong-Il, 68, is widely reported to be preparing to name his youngest son as eventual successor.

The sinking has sharply raised tensions on the peninsula. Gates and his South Korean counterpart Kim Tae-Young Tuesday announced a major joint naval exercise starting this Sunday as a deterrent to the North.

The South`s defence ministry said it would be the first in a series of about 10 joint naval drills in coming months. Gates defended the exercises as important to show resolve "not to be intimidated".

Clinton and Gates earlier Wednesday held talks with the South`s Foreign Minister Yu Myung-Hwan and Defence Minister Kim, the first such "two plus two" meeting in Seoul.

In a joint statement they warned the North of "serious consequences" for future aggression and urged the secretive state to admit it torpedoed the Cheonan.

Clinton said the new US sanctions aimed "to increase our ability to prevent North Korea`s proliferation, to halt their illicit activities that help fund their weapons programmes and to discourage further provocative actions".

They were designed to curb the North`s sale and procurement of weapons and related material, the procurement of luxury goods and other illicit activities.

They would strengthen enforcement of UN Security Council resolutions passed after the North`s nuclear and missile tests, and provide new authority to target illicit activities, she said.

The US would also strengthen efforts to "identify, pressure and put out of business North Korean entities involved in proliferation and other illicit practices overseas".

Clinton said the State Department and the Treasury would designate more entities and individuals supporting proliferation and freeze their assets.

There would be new efforts with key governments to shut down North Korean trading firms engaged in illicit activities and to prevent banks in overseas countries from handling illicit transactions.

Earlier Wednesday Clinton and Gates paid a joint visit to the border with the North in a symbolic show of support.

Watched through the window by a curious North Korean soldier, they entered a meeting room straddling the borderline at the border truce village of Panmunjom. They briefly set foot on the North`s side of the room.

Unlike the rest of the heavily fortified Demilitarised Zone (DMZ) bisecting the peninsula, the border at Panmunjom is marked only by a low line.

"It struck me that although there may be a thin line, these two places are worlds apart," Clinton told reporters.

"The Republic of Korea (South Korea) has made extraordinary progress. In contrast, North Korea has not only stagnated in isolation, the people of the North have suffered for so many years."

Clinton said the Obama administration continued "to send a message to the North that there is another way", referring to US pledges of major aid if Pyongyang scraps its nuclear weapons programme.

BDST: 1527 HRS, July 21, 2010