SEOUL, South Korea — Park Geun-hye, the embattled South Korean president, has decided to postpone a summit meeting with President Obama in Washington that had been planned for next week, her office said on Wednesday.

Her decision came amid mounting criticism that her government had allowed the outbreak of Middle East respiratory syndrome to become the biggest outside Saudi Arabia, where the disease was first discovered.

In South Korea, 108 cases had been confirmed by Wednesday, and nine people had died.

The criticism against her administration, even from within her governing Saenuri Party, was especially humbling for Ms. Park.

When the disease, known as MERS, hit the country last month, her government was still struggling to regain the confidence of South Koreans who remained shocked by the sinking of the ferry Sewol in April of last year. The sinking killed 304 people, most of them teenagers.

The large death toll was often blamed on the lack of a quick and efficient early rescue effort by the government.

As the number of MERS cases has steadily increased in the past two weeks, the president’s approval ratings have plunged below 40 percent, according to recent surveys.

“President Park has been mobilizing all national resources to deal actively with the MERS outbreak,” Kim Sung-woo, Ms. Park’s senior secretary for public relations, said during a news briefing on Wednesday. “Nonetheless, given the anxiety among the people over the situation, she has postponed her plan to visit the United States.”

Ms. Park had planned to visit Washington from Sunday to June 18. She had hoped to discuss the growing nuclear and missile threats from North Korea and other issues with Mr. Obama.

Mr. Kim, the presidential aide, said Ms. Park had decided to give priority to ensuring the “safety of the people.” He said that South Korea had already consulted with Washington and that the two allies would reschedule the visit.

South Korea said on Tuesday that it would investigate all hospitalized pneumonia patients to determine whether they had been exposed to the disease.

MERS symptoms are similar to those of pneumonia.

Nearly 2,900 people who had been near any of the confirmed cases were isolated as of Tuesday, to be monitored for symptoms by the government. More than 2,200 schools remained closed.

The government said that it would interview all hospitalized pneumonia patients on Wednesday and check their medical records to see if they had recently visited any of the hospitals where the infection had been found. South Korea’s first MERS case, a 68-year-old man who had traveled to Saudi Arabia and neighboring countries, was discovered to have the virus on May 20.