— The Obama administration opened the door for the first time Sunday to Iranian participation at the Syrian peace talks in Switzerland later this month.

Softening the former hard line against any role for Iran if it refuses to endorse the Jan. 22 conference ground rules, Secretary of State John F. Kerry suggested that Iran might be able to participate from the sidelines.

“Could they contribute from the sidelines? Are there ways for them conceivably to weigh in?” Kerry said of the Iranians, who oppose the conference’s goal of establishing a transitional government in Syria, its ally and neighbor.

Kerry suggested that Iran’s diplomatic office in Geneva might be able to help as an unofficial participant.

The United Nations envoy organizing the conference, Lakhdar Brahimi, wants Iran included in the talks, and U.N. officials have suggested that Iran might be able to play an unofficial role.

“It may be that that could happen, but that has to be determined by the secretary general,” Kerry said, referring to U.N. Secretary General Ban Ki-moon. “It has to be determined by Iranian intentions themselves.”

Kerry spoke during a conference in Israel, where he has spent several days prodding the Israelis and Palestinians to outline a peace deal he hopes to conclude this spring. Israel considers Iran its mortal enemy, and Prime Minister Benjamin Netanyahu opposed the deal Kerry helped strike with Iran, the United States and other nations over its nuclear program last year.

Though U.S. relations with Iran have improved since the successful early negotiations over Iran’s nuclear program, the United States remains suspicious of Iran’s foreign policy goals in Syria and elsewhere.

Kerry also stressed that the United States has not backed off its demand that all participants in the conference agree that the goal will be arrangements for a transitional body in Syria. France also insists on that precondition, and U.S.-backed Syrian opposition groups have reservations about Iran’s participation. Some opposition groups are boycotting the conference altogether.

“In terms of a formal invitation or participation, that is for those who support the Geneva 1 implementation," Kerry said, referring to the June 2012 adoption in Geneva of the transitional government proposal.

The United States and other nations backed the Geneva plan, seeing it as a way to ease Syrian President Bashar al-Assad from power. Though that plan does not stipulate that Assad must leave, it calls for the transitional authority to be chosen by mutual agreement of the Assad government and the political opposition.

Assad has agreed to send representatives to the conference this month but is not expected to voluntarily relinquish any power. Iran backs Assad as the legitimate leader of Syria, and has provided him with weapons and other military help during the nearly three-year-old conflict.