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LONDON — State of Secretary John Kerry said Wednesday he would not be distracted by "external factors or politics" as Western powers tried to forge a deal to curtail Iran’s nuclear program.

Kerry’s comments come a day after Israeli Prime Minister Benjamin Netanyahu told Congress that a potential deal “paves Iran’s path to the bomb,” and the world was better off without it.

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But Kerry said a deal was the best way to limit Iran’s nuclear capabilities, and nobody had yet presented a viable alternative. Netanyahu’s address to Congress at the invitation of GOP leaders was seen by some Democrats as a way to undermine the Obama administration’s attempts to secure a deal.

“Simply demanding that Iran capitulate is not a plan,” Kerry said from the Swiss resort town of Montreux, where negotiations have been taking place.

Kerry said that while progress had been made in the negotiations, “there are still significant gaps and important choices that need to be made.”

"We also want an agreement that is sustainable over time, and particularly that achieves the singular goal of proving that Iran's nuclear program is and will remain peaceful. We aren't going to be distracted by external factors or politics."

Kerry will fly to the Middle East on Wednesday where he will meet with leaders from Gulf nations about the nuclear talks.

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