MANILA - The Senate's version of the death penalty bill may cover only "high-level" drug trafficking to court more supporters in an "equally" divided chamber, Majority Leader Vicente Sotto III said Thursday.

Half of the 24-man chamber expressed support for the death penalty while the other half is against it, he said.

"Pagka drugs lang at high level, malaki ang pag asang ito'y makapasa," he told ABS-CBN News.

Sotto said he is willing to sponsor the bill and defend it on the floor because the justice committee chairman, Sen. Richard Gordon, is against the death penalty.

Sotto said proponents of the bill would try to have it passed by June this year.

The battle over the death penalty bill essentially shifts to the Senate after the House of Representatives on Wednesday passed its version on second reading, despite strong opposition from church and human rights groups.

A vote on third and final reading set next week will be a "mere formality," said Albay Rep. Edcel Lagman, who challenged the bill in plenary.

"The House leadership ran amuck in their unconscionable railroading of the death penalty bill," he told ABS-CBN News.

"I feel very strongly that the House leadership is not really concerned about the death penalty. It is just using the death penalty as an instrument to blindly support the President's deadly war against the so-called drug menace."

• Lagman vows to oppose 'watered down' death penalty bill

Lagman said he would go to the Supreme Court if the death penalty bill is passed into law.

"That is the last option but that is a very important option," he said insisting that such a law would be a "gross violation" of a treaty signed by the Philippines.

Under Second Optional Protocol to the International Covenant on Civil and Political Rights, the Philippines agreed that "no one within (its) jurisdiction... shall be executed."

Lagman argued there were no "compelling reasons" to reinstate the death penalty, one of the conditions set by law.