US President Barack Obama continued to offer Iran "serious, meaningful dialogue," despite revelations it was building a second secret nuclear facility, but warned Saturday that Teheran "must pursue a new course or face consequences."While Obama also stressed in his morning radio address that "Iran's leaders must now choose - they can live up to their responsibilities and achieve integration with the community of nations," members of Congress indicated they were already working to intensify steps to slap further sanctions on Iran.US Senators Joseph Lieberman, Evan Bayh and Jon Kyl as well as US House Foreign Affairs Committee Chairman Howard Berman announced Friday, soon after they were briefed on the development, that they were moving on legislation they had sponsored to cut off petroleum imports to Iran."The discovery that Iran has been hiding a secret uranium enrichment facility adds fierce new urgency to the collective, comprehensive effort to stop Iran's nuclear breakout," the senators said in a joint statement."In the absence of immediate compliance by Iran with the IAEA [International Atomic Energy Agency] and multiple UN Security Council resolutions, we must act swiftly and decisively to impose crippling new sanctions against Iran."US officials noted that they were working with Congress on the issue, something they have not emphasized before, as part of the strong consensus in the United States and beyond on the threat posed by Iran.In his radio address Obama declared that "the international community is more united than ever before," pointing to his conversation with Russian President Dmitry Medvedev on Wednesday.Russia, which was briefed on the secret facility at that time, is a key player in any international sanctions efforts and has traditionally expressed skepticism on their utility. But following Wednesday's meeting, Medvedev gave some endorsement for the idea.Obama made the initial announcement alongside his counterparts from Britain and France, close allies who cooperated on the intelligence-gathering and presentation of the information to the other countries and the IAEA, according to senior administration officials.All three countries pushed for a vigorous IAEA investigation, whose preliminary steps are already under way, with France and Britain articulating the firmest stand on the new sanctions Iran could face.French President Nicolas Sarkozy gave a December deadline for evaluating Teheran's response to diplomatic outreach efforts."We cannot let the Iranian leaders gain time while the motors are running. If by December there is not an in-depth change by the Iranian leaders, sanctions will have to be taken," Sarkozy said. "This is for peace and stability."And British Prime Minister Gordon Brown underscored, "We will not let this matter rest, and we are prepared to implement further and more stringent sanctions."Senior administration sources said Friday that Israeli officials had also been briefed on the discovery of the secret facility. "They are aware of the facility and the announcement that we're making today," one official said on Friday."I think it is fair to represent that they see that this path is obviously advancing our interest in delaying the Iranian nuclear program."