Sen. Marco Rubio cast doubt on the prospects for immigration reform passing Congress this year, despite a renewed effort by House Republicans to address the issue.

The Florida Republican, a possible 2016 presidential candidate, was a key negotiator of the bipartisan immigration reform legislation that cleared the Senate in June. But Rubio said a deep lack of trust in President Obama to uphold the border security measures likely to be included in any final deal stands in the way of attracting the Republican votes needed to send a bill to the White House.

In a brief interview with reporters Monday evening, Rubio didn't appear skeptical of the immigration reform principles that House Republican leaders presented to their members during last week's annual policy and political retreat.

Those principles mirrored much of what Rubio pushed in the Senate bill. Rather, Rubio indicated that Obama's willingness to unilaterally delay or alter some portions of Obamacare has left conservatives convinced that he would ignore any new border enforcement upgrades they win as a part of legislative negotiations. Following is a partial transcript of Rubio's comments on what the new action on immigration by House Republicans means for reform:

The biggest impediment to making progress on immigration that I’ve seen over the last year — and it’s one of the bigger lessons from the process that we undertook last year, is a complete lack of confidence that the law will be applied, that the enforcement measures will ever happen. And I think that’s only been exacerbated by the actions the president and this administration have taken over the last year. I don’t know how they overcome that.

The details of any legislation, I think, are largely going to depend on whether people can believe that this administration will enforce the law, or not. And, right now, the biggest complaint that I get from people on this law, is, they do not believe — no matter how good the enforcement measures might be — they do not believe that the federal government will actually put those in place. And, therefore they believe that this issue of having people in this country illegally will only lead to more people coming illegally in the future.

The “gang of eight” legislation that Rubio helped shepherd through the Senate included legalization of illegal immigrants and a 10- to 15-year path to citizenship. The principles of immigration reform announced by House GOP leaders discusses vague support for legalizing illegal immigrants after border security triggers are achieved.