US Secretary of State Hillary Clinton on Thursday proposed holding a regional conference on Afghanistan on March 31 that would likely include Iran. If Iran were to attend, it would mark an opening in relations between the Islamic republic and the Obama administration, which has been exploring ways of engaging with Teheran. The conference would be held under the auspices of the UN and look at ways of harnessing international efforts to improve the situation there. "Iran borders Afghanistan. In the early days of the military efforts by the United States and our allies to go after the Taliban and al-Qaida, Iran was consulting with our ambassador on a daily basis," Clinton told reporters in Brussels. "Where it is appropriate and useful for the United States and others to see whether Iran can be constructive, that will be considered." Robert Wood, the State Department spokesman traveling with Clinton, later said, "I would expect that Iran would be invited" to the regional conference. The development came the same day that US Senate Foreign Relations Committee Chairman John Kerry held a hearing on American policy toward Iran, in which he said, "If ever there was an urgent challenge that will require a multi-dimensional solution, surely it is Iran's nuclear program." He praised the idea of talking to Iran, saying, "We must engage directly with Iran, and I'm glad that this idea's day is coming." But he cautioned, "We must be honest with ourselves: We will not solve this problem just by talking directly to Teheran. While Iran was just talking to the IAEA and the Europeans, it deftly sidestepped every supposed red line laid down by the international community. While Iran was just talking to the world, it moved to the threshold of becoming a nuclear-capable state." The committee heard testimony from two former US national security advisers, Zbigniew Brzezinski, who served under Jimmy Carter, and Brent Scowcroft, who worked for George H.W. Bush. Brzezinski began by stressing actions that US shouldn't take, to avoid prejudicing the negotiations, arguing against ratcheting up sanctions, threatening the use of force, speaking of regime change and setting deadlines for the negotiations, unless the aim was for the talks to break down and for America to be able to blame that breakdown on Iranian intransigence. Accordingly, he criticized a story in Haaretz this week that said Israel told Clinton to impose a time frame on talks for them to have impact. "We should be very careful not to become susceptible to interested parties" and their policies on Iran, he warned. He also took issue with Israel's contention that a nuclear-armed Iran would be an "existential threat," and argued that deterrence in the form of extending America's nuclear umbrella to friends in the Middle East should allay Jerusalem's concerns. The US, Brzezinski maintained, faced more of an existential threat from the Soviet arsenal when he was in the White House, in the 1970s, than Israel did now, and deterrence proved effective in that case. Both Brzezinski and Scowcroft agreed that the biggest threat came not from Iran acquiring a nuclear weapon but from the impetus such an acquisition would give to a regional nuclear arms race. Many pro-Israel figures have assailed Brzezinski and Scowcroft for their views on the Middle East, and the choice to invite the two to testify did not sit well with several activists. "The choice of Brzezinski and Scowcroft sent up two yellow flags when I heard they were given such prominence," one Jewish leader said of Thursday's hearing. "When Brzezinski used his short opening statement to say Secretary of State Hillary Clinton should be cautious about listening to Israel's ideas, the red flag really went up. After all, Israel knows an awful lot about Iran and what they do that's against the interest of peace." AP contributed to this report.