Philippines and Cambodia in South China Sea row
The Philippines has summoned Cambodia's ambassador over comments linked to Manila's territorial row with Beijing.
Hos Sereythonh was asked to explain remarks accusing the Philippines and Vietnam of playing "dirty politics" over the issue of Asean and the South China Sea.
Mr Hos made the comments in a letter to the Philippine Star newspaper.
But he did not turn up on Tuesday, saying that he was sick, said foreign department spokesman Raul Hernandez.
"We will continue to summon him until he is able to come," Mr Hernandez said.
China has overlapping claims with four Asean members in the South China Sea.
At a regular meeting hosted by Cambodia last month, the 10-nation bloc for the first time in its 45-year history failed to issue a joint statement because of tensions over the maritime disputes.
In the published comments, Mr Hos accused the Philippines and Vietnam of attempting to "sabotage and hijack the joint communique" during the Asean meeting.
In his letter, Mr Hos said he was responding to an article written by an official of Philippines Department of Foreign Affairs on what happened at the Asean meeting.
The Philippines has accused Cambodia, a close ally of China, of blocking any mention of the South China Sea spat.
Meanwhile on Tuesday the Philippine government received bids for offshore oil and gas exploration in three areas off Palawan island that are also claimed by China.
"All the areas we have offered are well within the 200 nautical mile exclusive economic zone of the Philippines under the UNCLOS (United Nations Convention of the Law of the Seas)," said Jose Layug, an undersecretary in Manila's Department of Energy.
"Thus the Philippines exercises exclusive sovereign rights and authority to explore and exploit resources within these areas to the exclusion of other countries."
The bids would be evaluated and officials would award contracts within 100 days, he said.
China lays claim to a U-shaped swathe of the South China Sea, overlapping areas claimed by the Philippines, Vietnam, Taiwan, Brunei and Malaysia.
There are thought to be significant oil and gas reserves below parts of the South China Sea subject to ownership disputes.
In recent years tensions over the issue have increased amid growing assertiveness from China over its maritime claims.
Ties between China and the Philippines are already strained in the wake of a recent stand-off over another disputed area, the Scarborough Shoal.