U.S. President Barack Obama will spend much time and effort expressing sympathy over the loss of people in a tragic ferry sinking when he visits Seoul later this week, a White House official said Monday.

"I can certainly expect that this will be a big part of his trip," Ben Rhodes, deputy national security adviser for strategic communication, told reporters. "I'm sure the president will want to find a way to express to those families and to the people of the Republic of Korea how much we support them in this difficult time."

The Obama team will keep close tabs on how search-and-rescue efforts will unfold in the coming days, added Rhodes.

Obama plans to arrive in Seoul on Friday after a three-day trip to Japan.

South Korea is gripped by shock and sorrow from the sinking of the South Korean ferry near the southwestern tip of the peninsula Wednesday (local time).

Nearly 90 people are confirmed dead and more than 210 others remain missing.

Last week, Obama issued a statement offering condolences to the families of the victims.

The president said it's heart-wrenching to see Koreans going through such a tragedy.

He pledged full support for the South Korean government dealing with the ferry disaster.

USS Bonhomme Richard, an amphibious assault ship, is already helping the search of survivors.

The Pentagon announced it is also sending a salvage ship, USNS Safeguard, toward the peninsula from Thailand in case it is needed.

On his visit to Seoul, which would be his fourth as the U.S. leader, Obama also wants to assure South Koreans of Washington's unswerving security commitment, another key presidential aide said.

His message to South Korean President Park Geun-hye and the people there is basically four words: "We are with you," said Evan Medeiros, senior director for Asian affairs at National Security Council.

"So that means that we're going to do everything possible to ensure that our alliance with the ROK remains rock solid," he said.

He added Obama-Park summit agenda items would include Seoul's request for a further delay in the transfer of wartime operational control and its move to expand non-military nuclear programs.

Medeiros and Rhodes provided a preview of Obama's upcoming Asia tour in a briefing hosted by the Washington Foreign Press Center.

Obama's weeklong trip from Tuesday will also take him to Malaysia and the Philippines.

It is the latest manifestation of the president's firm commitment to his policy of Asia-Pacific rebalancing, Medeiros emphasized.

He dismissed a growing criticism that the Obama administration's Asia strategy is just rhetoric, not reality.

"There are often questions raised about whether or not we get distracted with Ukraine or the Middle East, and this trip is yet one more example that we can walk and chew gum at the same time," the official said.  (Yonhap)