Authorities have noticed that bomb attacks have been carried out every six months, Gonzales said.
The last was in February in which 13 people were killed and over a hundred wounded in bombings in the cities of Davao, General Santos and Makati.
Gonzales suspects the Abu Sayyaf, which claimed responsibility for the Valentine’s Day bombings, and another militant group known as the Rajah Solaiman Revolutionary Group may carry out the next attacks with help from Jemaah Islamiyah, al-Qaeda’s arm in Southeast Asia.
"We believe that the bombings have a cycle and we have noticed that it’s every six months. The last was in February. We expect bombings this month and next month," Gonzales said in an interview with Vice President Noli De Castro on his weekly radio program "Para Sayo... Bayan."
Gonzales raised concern over the failure of Congress to pass an anti-terrorism bill. Several similar measures have been awaiting legislative action for the past months.
An anti-terrorism law would enable authorities to detain suspects for longer periods without charges, among other things. Stiff penalties are also sought for those found guilty.
As of now, terror suspects are merely slapped with charges of illegal possession of explosives, which is a bailable offense.
Gonzales, however, expects continued inaction on the pending anti-terrorism bills because of the raging political bickering between the Arroyo administration and the opposition.
He speculated that the opposition might view Malacañang’s push on the anti-terror measure as a diversionary tactic to delay the ongoing impeachment proceedings against Mrs. Arroyo, who is accused of cheating in last year’s presidential election.
"That is how politics goes in our country — they will suspect that this is a diversionary tactic," Gonzales said.
He cited a similar incident a few weeks ago when he issued a warning and raised the possibility of a huge terrorist attack.
"When I said the terrorists are planning to use 1,000 kilos of explosives, they said I might be the one who will detonate it," he said.
Thousands of bills in the Senate and the House of Representatives have been put on hold because lawmakers have been busy attacking or defending Mrs. Arroyo.
Authorities had seized 600 kilos of explosives from a suspect in the attacks last February. However, he was freed after posting bail of P300,000.
"We discovered that they were planning to build a superbomb. They’ll use 1,000 kilos of explosives," Gonzales said, adding that they suspected the explosives would be used to attack the US Embassy in Manila.
Although the US Embassy is tightly guarded, a bomb that powerful could severely damage the complex and kill hundreds of people if detonated, according to Gonzales.
"We found 600 kilos of explosives and arrested the suspect, who is now out on bail. That is why we are urging Congress to give its attention to the anti-terrorism bill."
Gonzales said if terrorists could amass a huge amount of explosives, it may also be possible for them to use biological or small nuclear weapons in the future, which Gonzales admits Philippine security forces are not trained to deal with.
Authorities have been hunting for six suspected foreign terrorists on Philippine soil who may be plotting to launch attacks across the country.
Gonzales said they are among 10 suspected suicide bombers who reportedly slipped into the country in recent weeks according to information furnished by Indonesian intelligence authorities. All 10 suspects allegedly have ties with Jemaah Islamiyah.
London was targeted recently for being a US ally, he said. "And here in our region, the Philippines and Australia" may be major targets as well because of the two countries’ close US ties.
Maguindanao Rep. Simeon Datumanong, chairman of the House committee on justice, has assured the public that the anti-terrorism bill will be passed before yearend.
Datumanong said the justice committee met last week and held its last public hearing on the anti-terrorism bill now pending before his panel, which is also handling the impeachment complaint against Mrs. Arroyo.
Committee members have agreed to hold one more meeting on the bill before sending it to the entire House for deliberations.
"I’m certain that before the end of September, we’ll make a report to the plenary. By October, it’ll be on second reading and debate in the House of Representatives," Datumanong said.
He assured that the impeachment complaint and the renewed drive to amend the Constitution would not delay the passage of the anti-terrorism bill.
Gonzales stressed public support is very important for the passage of the measure because the administration might be accused of using the bill to delay the impeachment complaint as well as the proposal to amend the nation’s Charter.
The bombings last February were the worst terrorist attacks in the Philippines since the February 2004 sinking of the SuperFerry 14, in which over a hundred people were killed.
A bomb believed planted by the Abu Sayyaf started a fire that sank the vessel in Manila Bay.