MANILA, JULY 27 (MONDAY) -- The Philippines' new Congress officially opened today, marking the next-to-last step in the country's delicate passage from strongman rule to democracy.

The 200-member House and 24-member Senate held separate ceremonial sessions this morning and were to sit jointly this afternoon for an address by President Corazon Aquino.

Both houses, led by aggressive veteran lawmakers, are expected quickly to assert their independence from Aquino as they try to redefine the balance of power and seize the political initiative from Malacanang palace.

Senate President Jovito Salonga and Speaker of the House Ramon Mitra, despite being Aquino allies and having served in her original Cabinet, have made clear in outlining their own legislative agendas that they have no intention of being a rubber stamp.

In fact, they specifically asked Aquino not to pass by decree a number of legislative initiatives. Included in these was her controversial land reform law that she signed last week ordering most of the country's agricultural estates dismantled and distributed among the Philippines' 2 million peasants.

Aquino has had lawmaking powers since the disbanding almost a year and a half ago of the previous legislature, so packed by allies of deposed president Ferdinand Marcos that it has been called the "national kennel." Under the Philippines' U.S.-style constitution, the president has no lawmaking powers; she can only sign or veto laws passed by Congress.

So far, Aquino has given no indication whether she intends to be an activist president lobbying for her own programs with the new Congress or to adopt a more passive role. Some observers believe that Aquino, who is still immensely popular in the country, would prefer to become a figurehead president, leaving the professional politicians in Congress to actually run the government. At her last news conference, Aquino refused to answer a question about whether she would personally lobby for her programs, specifically her land reform measure.

Her previous executive orders, including the land reform decree, could be overturned by Congress' passage of its own laws. In fact, in her land reform measure she left it to Congress to decide on some of the thornier issues, such as the acreage that landowners will be allowed to retain for their own use and the deadline for completing the massive redistribution.

"If President Aquino does not beware, she may soon find that the initiative to lead the nation will be grabbed by Congress," respected columnist Amando Doronila wrote recently in the Manila Chronicle. "If Mrs. Aquino does not act swiftly enough to stop the eroding base of her leadership, she will soon be reduced to a reactive president rather than a creative one. . . . She will eventually find that, through unwitting abdication, she has become a hostage to Congress, unable to govern effectively."

Yesterday, on her final day of governing with near-absolute powers before Congress convenes, Aquino issued 42 presidential decrees. In the past few days she has rammed through a raft of more than 60 new measures by executive orders. Some of the more significant ones were pushed through because of pressure from influential groups, such as the military; many of the measures were administrative matters, such as reorganizing government departments.

In one of her last decrees, Aquino set Nov. 9 as the date for local elections to replace the thousands of appointed mayors, governors and councilmen around the country who are holding their jobs on an interim basis. The election will mark the final step in the Philippines' transition from the Marcos era.

In other decrees yesterday, Aquino revived a subversion statute that specifically names the Communist Party of the Philippines as "an organized conspiracy to overthrow the government." The existing statute did not name the Communists. She also increased the maximum penalty for rebellion from 12 years to life in prison, as has been demanded by the powerful military, and created a volunteer citizens' corps of reservists to supplement the professional armed forces.

The military, fearing possible attempts to disrupt the opening of Congress, has placed its forces on maximum alert in the city and surrounding provinces.

Leftist groups and right-wing Marcos loyalists have planned major demonstrations for the opening of Congress.

Despite the presence of many legislative veterans in the new Congress, it will be the youngest in the Philippines' history, and more than two-thirds of its members will be newcomers to the political arena. Lawmakers have made much of the Congress' youth and fresh faces as evidence of a break with the past. Thus, symbolically, Speaker of the House Mitra chose the House's youngest member, 27-year-old Gerardo Roxas, to formally open today's inaugural session.

Old politics versus new already has provided the first major source of tension within the Congress during debates over leadership and the selection -- as opposed to election -- of powerful committee chairmanships. Both Salonga and Mitra are old-school politicians, and they already have been criticized by new, young reformists for filling key positions through back-room deals instead of open competition among the members.

Aquino is scheduled to deliver a state-of-the-nation address to a joint session of the new Congress late this afternoon. Many foreign dignitaries, including Rep. Stephen J. Solarz (D-N.Y.), arrived here over the weekend to attend the opening.