In a statement, Presidential Spokesman Ignacio Bunye said the decision of Drilon and Villar to divide the term of the Senate presidency will preserve unity in the 14-member Senate majority.
"We see the agreement as a stroke of wisdom and statesmanship," he said.
"This will pave the way... for the speedy passage of legislative measures of urgent impact to the Presidents agenda and the national interest."
Under the agreement, Drilon will serve in the First and Second Regular Sessions of the 13th Congress, beginning July 26.
Villar will start his term in July 2006, when the Third Regular Session begins.
Malacañang sources said Drilon, who is on his second and last term, might later be named executive secretary or secretary of foreign affairs by President Arroyo.
Villar, who will seek re-election in 2007, would come in as Senate president to carry the brunt of Charter change, which Mrs. Arroyo has been pushing with the help of her allies in Congress.
On the other hand, Sen. Aquilino Pimentel Jr. said yesterday the power-sharing agreement between Drilon and Villar will bring "bad luck" to the two senators.
Pimentel said the late senator Renato Cayetano, who had a similar deal with Drilon, did not live to serve half of the Senate presidents term.
"I am warning Senator Villar that Senator Cayetano did not fare very well under that kind of agreement," he said.
Pimentel said the Drilon-Villar agreement will impair the right of the other senators to choose the next Senate president.
"I think that is violative of public policy," he said. "When there is horse trading for public office, that is tantamount to selling a position."
Pimentel said the eight senators present during an opposition caucus last July 7 had reached a consensus to vote as a bloc in the Senate presidents election.
"We believe that the minority would be in a better position to protect our right if we will act as one," he said.
Pimentel said minority senators will scrutinize the actions of Mrs. Arroyo to prevent her administration from pursuing policies inimical to public interest.
"We are committing ourselves to preserve our unity in the face of Malacañangs attempts to break (our) ranks even at this early stage," he said.
He has spurned Malacañangs overtures for an alliance because he could not turn his back on the electoral mandate to play a fiscalizers role, Pimentel added.
Meanwhile, the Presidential Legislative Liaison Office (PLLO) has started preparations for Mrs. Arroyos State of the Nation Address (SONA) before a joint session of Congress on July 26.
A PLLO official said Mrs. Arroyo might call a workshop of the Legislative-Executive Development Advisory Council (Ledac) with all Cabinet officials to thresh out the common legislative agenda consistent with the administrations 10-point legacy program.
"The soonest would be Wednesday after July 26 so (Congress) would have one day to chew on the Presidents SONA," said a PLLO official.
"Hopefully, by then both chambers have already organized themselves with the committee chairmen and proper appreciation of the Presidents SONA."
The official said the executive branch will hold a similar workshop before the SONA to brainstorm on how to shape the 10-point program and legislative agenda.
"What are the legislative measures to pursue and executive actions desired to complement (them) ... what are the doables and realist goals," the official said.
Economic Planning Secretary Romulo Neri, who heads the Ledac secretariat, would be in charge of the workshop with the PLLO providing technical support.
Leaders of the business sector, academe and "civil society" will be invited to the workshop. Marichu Villanueva, Jose Rodel Clapano