Speaking to reporters, Kerry inveighed against what he sees as a tendency within the United States to retreat from the world even as he defended the Obama administration's diplomatic efforts from Syria to the Israeli-Palestinian conflict.
In comments tied to the budget that U.S. President Barack Obama is expected to present on Tuesday, Kerry suggested that tighter spending, in part at the behest of congressional Republicans, may limit U.S. clout around the world.
"There's a new isolationism," Kerry said during a nearly one-hour discussion with a small group of reporters.
"We are beginning to behave like a poor nation," he added, saying some Americans do not perceive the connection between U.S. engagement abroad and the U.S. economy, their own jobs and wider U.S. interests.
Kerry made the case as Obama prepares to release a budget that will adhere to spending levels agreed to in a two-year bipartisan budget deal struck late last year, entailing some spending cuts the administration would have preferred to avoid.
The U.S. State Department budget will decline slightly in the president's budget submission, Kerry said, saying this was a direct result of the bipartisan budget deal that cut funding further than Obama wanted.
"This is not a budget we want. It's not a budget that does what we need," he said, saying the budget deal entailed cuts demanded by the Republican-led House of Representatives. "It was the best the president could get. It's not what he wanted."
In speaking of what he called the "new isolationism," Kerry cited the limited support in the U.S. Congress to back Obama's plan to launch an air strike against Syria last year because of its suspected use of chemical weapons against civilians.
Obama, in a decision criticized by some U.S. allies in the Gulf and elsewhere, asked Congress to vote on a strike. With limited congressional backing, he ultimately abandoned a strike and pursued a deal to get Syria to give up its chemical weapons.
"Look at our budget. Look at our efforts to get the president's military force decision on Syria backed up on (Capitol Hill). Look at the House of Representatives with respect to the military and the budget," Kerry said.
"All of those things diminish our ability to do things," he added.
Kerry took particular aim at critics of his efforts to get the Syrian government and the opposition that has sought to oust Syrian President Bashar al-Assad for nearly a year to reach a peace agreement that would entail Assad's departure.
A second round of peace talks in Geneva broke up on Saturday, with chief mediator Lakhdar Brahimi lamenting a failure to achieve much beyond agreement on an agenda for a third round.
"These people who say that it's failed or that it's a waste of time ... Where is their sense of history" Kerry said.
"How many years did the Vietnam talks take How many years did Dayton take in Bosnia-Herzegovina" he added. "These things don't happen in one month. I mean it's just asinine, frankly, to be making an argument that after three weeks it's failed."
Kerry blamed the lack of a diplomatic resolution on the marked shift in momentum on the ground to Assad's forces, backed by Iran and by the Lebanese militant group Hizbollah, as well as on what he called "the opposition's machinations."
"The dynamics on the ground shifted and with that shift, I believe, came an additional ingredient ... which was the infighting of the opposition began to divert from the focus on Assad," he said.