"More than half of the population voted for the Constitution -- that's the requirement. Therefore, the threshold for amending the Constitution and especially Chapter 1 articles should not be lower than that. The president would definitely veto," Mindaugas Lingė, the president's internal policy adviser, told the Ziniu Radijas radio station.
Lowering the threshold of votes for Chapter 1, which defines the state's fundamental values, such its language, flag, capital, territorial integrity and sovereignty, would set "a negative precedent" and "unleash uncontrolled risks", the adviser said.
"The president believes that we don't need any artificial relaxing of the requirements. We need more preparation for the referendum and dialog with people," he said.
Under the proposed amendment to the Law on Referendum, a decision on amending an article of Chapter 1 and Chapter 14, which now have a higher level of protection, is deemed as adopted if at least two-fifths of all citizens having the right of vote say "yes" in a referendum.
Currently, approval from more than a half of all eligible citizens is needed to amend an article of the two chapters.
The Seimas plans to vote on the proposed amendment on Tuesday.
Around 2.5 million Lithuanian citizens have the right to vote.
The proposal to lower the threshold comes in preparation for a dual citizenship referendum planned to be held on May 12 and May 26, 2019, in tandem with the first and second rounds of voting in the next presidential election.
Currently, people who left Lithuania after it regained independence in 1990 cannot hold dual citizenship, apart from a few exceptions. That provision can only be amended by referendum.
Advocates of dual citizenship fear that such a referendum might fail due to low turnout unless the threshold is lowered.