WASHINGTON - US Democratic presidential front-runner Hillary Clinton has stepped attacks against her party rival Bernie Sanders as polls show him narrowing her lead in polls.

In a Democratic primary in Iowa that appears to be tightening, Clinton’s campaign has escalated its attacks on Sanders over his perceived inexperience with foreign policy, especially his call for normalizing relations with Iran. “This proposal to more aggressively normalize relations and to move to warm relations with Iran not only breaks with President Obama’s policy, it breaks with the sober and responsible diplomatic approach that’s been working for the United States,” Jake Sullivan, Clinton’s senior policy adviser, told reporters in a conference call. 

“The proposal would not succeed, but it would cause very real consternation among our allies and partners,” Sullivan added. Speaking at a campaign rally in Indianola, Iowa, on Thursday, Clinton said that Sanders is mostly trying to avoid the issue of foreign policy.

“Sanders doesn’t talk very much about foreign policy, but when he does, it raises concerns because sometimes it can sound like he hasn’t really thought it through,” Clinton said.”The challenges a president has to grapple with are beyond complicated, both at home and abroad. That’s why it’s the hardest job in the world. I’ve seen it up close and personal and I know what it takes,” she added.