The Mexican government said on Monday that a border security fence approved by the US Congress to keep out unwanted immigrants would "damage" bilateral relations.
Mexican presidential spokesman Ruben Aguilar also said that the 1,125km barrier would create a "climate of tension" along the frontier.
"The Mexican government expresses its strong rejection of the construction of the wall ... This decision damages the entire bilateral relationship, is contrary to the spirit of cooperation that must prevail to guarantee the security of the frontier," said Aguilar, spokesman for President Vicente Fox.
The decision creates "a climate of tension among the border communities and creates splits instead of a convergence between the two countries," he said.
Speaking at a gala press dinner, president-elect Felipe Calderon, who assumes office on Dec. 1, said "neither decree nor physical barrier" will reduce migration across the border.
The US Congress on Friday approved construction of the wall along the border, which tens of thousands of mainly Latin American immigrants cross illegally each year.
The barrier is opposed by advocates of an easier immigration policy, but backed by many in the US who want a crackdown on the estimated 11.5 million illegal immigrants in the country.
"I understand the right of every country to determine its security and protect its territory, but two such clearly and inevitably complementary economies cannot be separated with a wall," said Calderon, of the conservative, pro-business National Action Party shared with outgoing president Fox.
Responding to criticism of the decision, US Assistant Secretary of State for Western Hemisphere Affairs Thomas Shannon asked for patience.
Construction of the wall will be part of a more multifaceted immigration reform, he said at a recent meeting of the Inter American Press Association.
"We ask you for patience. In the long run, what we will see is that we are going to have a series of measures that will be part of a much broader immigration reform," he said.
The Mexican government will send "a diplomatic note describing our position" following the decision by the US Congress, Aguilar said.
The bill approving the wall was motivated by Nov. 7 legislative elections, he said.
"The partial measure, exclusively concentrated on security, denies reality and represents in the current context more of a political response than a viable solution to the problem," Aguilar said.