MANILA, Philippines -- Senator Miriam Defensor Santiago cautioned her peers on Tuesday against tinkering with the country's territorial limits with a new baseline bill declaring the Philippines as an archipelagic state because it would reduce, not expand, the country?s territory and would require a change in the Constitution.

In a statement, Santiago said the Philippines would be entitled to only 12 nautical miles of the territorial sea under the United Nations Convention on the Law of the Sea (Unclos).

?If the Philippines declares itself an archipelagic state, our zone of sovereignty would collapse. Our internal waters would become archipelagic waters where the ships of all states will enjoy the right of innocent passage,? she said.

?In addition, foreign states would have the right of so-called archipelagic sea lane passage. Ships of all states would have the right of passage and their aircraft would have the right of over flight. This is an almost colossal reduction from the wider boundaries of the International Treaty Limits under the Treaty of Paris,? said Santiago.

Santiago, chair of the Senate foreign affairs committee, said that the Constitution already defined the national territory comprising the Philippine archipelago and all other territories over which the Philippines asserted sovereignty or jurisdiction.

"The Constitution does not describe the Philippines as an archipelagic state, which is a term of art used by the UN Convention. If the Philippines declares itself an archipelagic state, the declaration would contradict the Treaty of Paris which sets out the boundaries of our national territory, which are wider than those allowed by the Unclos,'' said Santiago.

As an archipelagic state, Santiago said the Philippines would have less enforcement jurisdiction on foreign vessels not only in matters of security but also marine pollution.

Santiago cited the 1898 Treaty of Paris, where Spain ceded the Philippines to the United States, as the basis for the present Philippine Baseline Law while "the bills pending in Congress will eliminate such limits and thus, the Philippines would lose its boundaries.''

Santiago said that the present bills seeking to extend the archipelagic baselines so as to include Scarborough Shoal would not be advisable, because it would revise the Treaty of Paris.

The Philippines would also have to get expert opinion to determine whether the Kalayaan island group or Spratlys "constitutes another archipelago.''

"Under Unclos, an archipelagic state can be composed of two archipelagos. If not, under international law, Kalayaan could be characterized as ?other islands? over which the Philippines is entitled to claim sovereignty,? she said. ?International law does not recognize the drawing of archipelagic baselines as a method of claiming territorial sovereignty.?

Instead of exerting the country's claim over Spratlys through a baseline bill, Santiago proposed that the government make an "effective occupation'' of the disputed islands.

?The Philippines has already exercised many political and administrative acts of a sovereign nature over Scarborough Shoal. Such acts include military exercises, establishment of lighthouse, enforcement of laws against foreign vessels and nationals, which are evidenced by historical data,? the senator said.

Santiago is also worried of the impact of the baseline bills on the country's claim over Sabah and warned against the wording of the pending bills concerning Sabah.

"If the pending bills abolish Sec. 2 of Republic Act No. 5446 which provides that the Philippines has acquired dominion and sovereignty over Sabah, North Borneo and hence, the baselines of the territorial sea include baselines of the territorial sea around Sabah, the effect is to remove from Philippine law the affirmation of sovereignty over Sabah," she said.

Santiago noted that in 2001, with Dean Merlin Magallona arguing for the Philippines, the International Court of Justice relied on Philippine law in referring to the dispute between Malaysia and Indonesia over Pulau Ligitan and Pulau Sipadan.

"The ICJ ruled that the Philippines will not in any way be affected by its decision on the merits in the case between Malaysia and Indonesia,'' said Santiago.

This is the reason, Santiago said, that a congressional commission on national territory should be established because the present bills ?do not fully appreciate the magnitude and depth of the country?s territorial problems."