WASHINGTON - More than a quarter of the Senate introduced legislation Thursday that could raise sanctions on Iran and compel the United States to support Israel if it launches a preemptive attack on the Iranian nuclear program, defying President Obama and drawing a veto threat.

The bill, sponsored by 13 Democrats and 13 Republicans, sets sanctions that would go into effect if Tehran violates the nuclear deal it reached with world powers last month or lets the agreement expire without a long-term accord. The measures include a global boycott on Iranian oil exports within one year and the blacklisting of Iran's mining, engineering, and construction industries.

The goal, according to supporters, is to strengthen the negotiating leverage of the Obama administration as it seeks to pressure Iran into a comprehensive agreement next year that would eliminate the risk of the Islamic republic developing nuclear weapons. But it could also create added complications for U.S. negotiators, who promised Iran no new economic sanctions for the duration of the six-month interim pact that was finalized on Nov. 24 in Geneva.

"Current sanctions brought Iran to the negotiating table, and a credible threat of future sanctions will require Iran to cooperate and act in good faith at the negotiating table," said Sen. Robert Menendez (D., N.J.), who spearheaded the effort with Sen. Mark Kirk (R., Ill.).

Kirk called the draft law "an insurance policy to defend against Iranian deception."

The Obama administration has furiously lobbied Congress not to impose new sanctions, even on a conditional basis, saying the increased economic pressure could force Iran to withdraw from the negotiating process and strain ties between the United States and its key negotiating partners - Britain, China, France, Germany, and Russia. Washington is banking on these countries to persuade Tehran into accepting a final package that would ease trade, financial, and oil restrictions if the Iranian government severely rolls back its uranium enrichment activity and other elements of its nuclear program.

Iran's foreign minister also has said new sanctions could scuttle hopes of a diplomatic resolution. Iran maintains its program is solely for peaceful energy production and medical research, but the United States and many other countries harbor severe doubts. Israel is perhaps most adamant in insisting Iran's true intentions are to develop an atomic weapons arsenal.

The White House said it didn't believe the Senate bill would be enacted and didn't think it should be enacted.

"We don't want to see action that will proactively undermine American diplomacy," press secretary Jay Carney told reporters.

State Department spokeswoman Marie Harf suggested the bill risked taking America closer to a potential military confrontation with Iran.

A Senate vote won't happen until January at the earliest, and it's unclear if the bill will have enough support. Majority Leader Harry Reid (D., Nev.) has effectively blocked the issue from being addressed before legislators adjourn for 2013.