WASHINGTON - Secretary of State John F. Kerry told Congress on Wednesday that any chance of resolving the Israeli-Palestinian conflict by creating a separate Palestinian state may be lost in two years.

The unusually specific prediction was intended to highlight Kerry's urgency in trying to encourage peace negotiations between Israelis and Palestinians.

"The window for the two-state solution is shutting," he said. "I think we have some period of time, a year and a half or two years, or it's over."

Some Arab officials and peace advocates have warned that continuing Jewish construction in the West Bank and East Jerusalem, which the international community views as illegal, and other factors, would one day make it impossible to create a viable Palestinian state. But specific predictions have been rare from U.S. officials.

Kerry's warning emphasized the pressure on Israelis and Palestinians, but also on the Obama administration, which would presumably want to avoid such a development on its watch. During a trip to Jerusalem in March, President Obama called upon Israelis to embrace a Palestinian state to guarantee their nation's future.

Kerry, a former senator from Massachusetts who became secretary of State this year, made no promises, saying only that he and his team were "committed to trying to find out what is possible."

He declined to provide details of his approach or planned schedule.

Robert Danin, a former U.S. diplomat now at the Council on Foreign Relations, said the most important factor for the Obama administration will probably not be construction or internal politics, but "the administration's ability to be effective on the world stage."

On a different subject, Kerry insisted to Republican lawmakers that American investigators are making progress in their examination of the attacks on the U.S. Consulate in Benghazi, Libya, that killed U.S. Ambassador J. Christopher Stevens and three other Americans in September.