"This motion is not aimed at destruction, but rather correction," said MP Abdi Barre Yusuf, who is backing the motion accusing President Hassan Sheikh Mohamoud of corruption.
The motion was filed earlier this week, and still has to be approved by the speaker before being put to parliament.
It is unclear how many support it, but lawmakers claim they have around 100 MPs behind it.
But while at least 90 members are needed for a motion to be debated in parliament, two-thirds of the 275-member house would have to back the vote to force the president from office.
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They include the United Nations, regional nations and the 22,000-strong African Union force (AMISOM), which is battling Somalia's Al-Qaeda affiliate, the Shebab.
In a joint statement, they expressed "deep concern that the parliamentary motion... Will impede progress on Somalia's peace and state building goals."
The statement was also signed by East Africa's regional IGAD bloc, the Inter-Governmental Authority on Development, as well as the European Union, Britain and the United States.
The Shebab still control large parts of the rural south and attacks at will in Mogadishu.
"The whole objective is to bring about change," Abdirahman Hosh Jibril, another lawmaker said.
International backers warned that efforts to impeach the president will "consume extremely valuable time, not least in the absence of essential legal bodies," the statement read.
"The submission of any such motion requires a high standard of transparency and integrity in the process," it added.
The current president and parliament were appointed by clan elders in 2012 with foreign backers promising full democracy in 2016, signalling an end to decades of chaos and instability.
But Somalia last month admitted that insecurity and lack of political progress means there cannot be elections in 2016 with individual suffrage as envisaged by the UN, foreign diplomats and the government itself.