US President Donald Trump has said "not nearly enough" progress is being made in negotiations with Mexico to avert his threatened tariffs.
Trump administration officials will meet for a second day of talks with Mexico's foreign minister in Washington tomorrow.
Mr Trump vowed import duties of 5 percent will take effect on Tuesday unless Mexico stems the flow of migrants to the US.
Those numbers reached their highest level in more than a decade last month.
US Vice-President Mike Pence and Secretary of State Mike Pompeo held talks with Mexican Foreign Minister Marcelo Ebrard at the White House on Wednesday, but the 90-minute meeting ended without agreement.
Mr Ebrard told a news conference afterwards the negotiations had been cordial, but tariffs were not even discussed.
"The dialogue was focused on migration flows and what Mexico is doing or is proposing to the United States, our concern about the Central American situation," he said.
The US president, who is in Europe for World War Two commemorations, warned on Twitter that the tariffs would go ahead next Monday if there is no breakthrough.
Under his proposal, duties would rise by 5 percent every month on goods including cars, beer, tequila, fruit and vegetables, reaching 25 percent by October.
Mr Trump wants Mexico to stop the hundreds of thousands of mostly Central American migrants who have been seeking entry to the US this year.
The US president announced the planned Mexico tariffs last week on Twitter, catching members of his own party and financial markets unawares.
White House trade adviser Peter Navarro had raised hopes earlier today of a possible rapprochement.
He told CNN "we believe that these tariffs may not have to go into effect, precisely because we have the Mexicans' attention".
Mr Navarro said Mr Trump wants Mexico to commit to take all asylum seekers and to divert more resources to its own southern border with Guatemala.
Mexican President Andrés Manuel López Obrador has said he is optimistic about defusing a potential trade war that analysts have said could tip his country's economy into recession.
Some commentators have speculated that Mr Trump will not follow through, pointing out that he reversed course on a threat to close the US-Mexico border in April.
But the US president insisted in a tweet on Tuesday he was not "bluffing". The US is already locked in a tit-for-tat tariff war with China.
Does Trump have political support for Mexico tariffs?
Some members of the president's Republican party in the Senate have threatened a rare revolt.
They have raised the possibility of banding together with Democrats to form a veto-proof majority against his plan.
But other Republican senators and members of the House of Representatives are sticking by Mr Trump on his signature issue.