Senator John McCain, Republican of Arizona, whose office organized the tour, said that while there has been progress, the border "is still not as secure as we want it to be or expect it to be".
Lawmakers have been pressing Homeland Security Secretary Janet Napolitano to devise a measure they can use to judge if the Obama administration's claims of significant progress in border enforcement are justified.
"We saw progress - the borders opened, there were attempts to get the Communists out of power.
Writing in Ireland's Sunday Independent newspaper ahead of a visit to the country on Monday, he said there will need to be "substantial progress" on the border issue by the next major meeting of EU leaders, who are due to assess progress on the border issue at a summit in June.
Two things need to be done.First, the slow progress towards a border settlement needs to resume.
That might not happen this year if the president leans heavily on the Pentagon to make progress on the border wall.
Such steps look calculated to cause offence.Broader relations have improved over the past couple of years, though with no progress on the border.
Khartoum is far from blameless in the oil dispute, unhelpfully linking its resolution to simultaneous progress on intractable border, security and debt issues.
Vice President Biden is expected to tout progress on strengthening border security and deepening economic ties when he meets Friday with the leaders of the Northern Triangle nations at the Inter-American Development Bank in Washington.
EU officials dismissed this as a non-starter, saying such a concept was predicated on the EU suspending the application of its own laws, which it did not consider "a sound basis" for progress on the border issue.
Seth Mydans (NYT) MIDDLE EAST LEBANON: PROGRESS SEEN ON BORDER -- The United Nations Middle East envoy, Terje Roed-Larsen, said that most of the remaining nine Israeli violations of the Lebanese border have been rectified and the rest should be resolved soon, which would open the way for the deployment of United Nations peacekeepers in southern Lebanon.
