YANGON, Myanmar — Myanmar's detained opposition leader Aung San Suu Kyi failed to retrieve food delivered to her home amid speculation she may have launched a hunger strike.

Nyan Win, spokesman for the National League for Democracy, said Tuesday he could not confirm whether Suu Kyi was refusing to eat, but said bags of food delivered Monday to a checkpoint outside her heavily guarded house were not picked up.

Suu Kyi has been under house arrest for 13 of the past 19 years, and she relies on the NLD's food deliveries for survival. It remains unclear whether Suu Kyi has launched a hunger strike since her supporters are barred from meeting her.

Burmese dissident groups based in neighboring Thailand said Monday she began a hunger strike on Aug. 15 and hasn't accepted food since.

"If Daw Aung San Suu Kyi continues to refuse food from her comrades, her health will be of serious concern," one group, the National League for Democracy (Liberated Area), said in a statement.

"Two people living with Daw Aung San Suu Kyi are also refusing food. The international community's immediate action is necessary," it said.

The news comes after Suu Kyi repeatedly canceled meetings with U.N. Special Envoy Ibrahim Gambari during his six-day visit to Myanmar that ended Saturday. He left without seeing her.

Since refusing to see Gambari, supporters have speculated that the Nobel Peace Prize laureate has grown more frustrated with the United Nations' failure to bring about change in the military-ruled nation.

Myanmar, also known as Burma, has been in a political deadlock since 1990, when Suu Kyi's party overwhelmingly won general elections, but was not allowed to take power by the military.

On Sunday, Nyan Win said Gambari had wasted his time in Myanmar. He also criticized the U.N. envoy for failing to meet the country's leader, Gen. Than Shwe, and for being unable to get any commitment from the junta to start talks with the opposition on national reconciliation.

Nyan Win also castigated Gambari for offering to help the junta prepare for planned 2010 elections.

Suu Kyi's NLD has criticized the planned polls, which follow a constitutional referendum earlier this year that critics say was neither free nor fair. The new constitution guarantees 25 percent of parliamentary seats to the military, and allows the president to hand over all power to the military in a state of emergency.