Zurich ? Turkey and Armenia signed a landmark agreement Saturday to establish diplomatic relations and open their sealed border after a century of enmity, as U.S. Secretary of State Hillary Rodham Clinton helped the two sides clear a last-minute snag.

The contentious issue of whether the killing of up to 1.5 million Armenians during the final days of the Ottoman Empire amounted to genocide is only hinted at in the agreement.

“There were several times when I said to all of the parties involved that this is too important,” Clinton said. “This has to be seen through. We have come too far. All of the work that has gone into the protocols should not be walked away from.”

The Turkish and Armenian foreign ministers signed the accord in the Swiss city of Zurich after a dispute over the final statements they would make. In the end, the signing took place about three hours later than scheduled and there were no spoken statements.

Clinton and mediators from Switzerland intervened to help broker a solution, U.S. officials said on condition of anonymity, in keeping with State Department regulations. Better ties between Turkey, a regional heavyweight, and poor, landlocked Armenia have been a priority for President Barack Obama, and Clinton had flown to Switzerland to witness the signing, not help close the deal.

The accord is expected to win ratification from both nations’ parliaments and could lead to a reopening of their border within two months. It has been closed for 16 years.