The U.N. Security Council met to discuss agreements signed by Sudan and South Sudan.
South Sudanese President Salva Kiir ordered his forces from the border ahead of setting up a demilitarized zone. South Sudan said it could have its forces redeployed within two weeks, urging Sudan to follow suit.
Rice, the U.S. ambassador to the United Nations, said a secure border is long overdue. South Sudan gained independence in 2011 as part of a peace deal that ended civil war but border skirmishes have threatened the peace.
If implemented, Rice said during a news conference, there are hopes for an advancement of mutual interests in the region.
"The United States' position, which we stressed and many other delegations did as well, is that there have been many agreements signed but too few actually implemented," she said.
Catherine Ashton, the foreign policy chief for the European Union, said the Sudan-South Sudan agreement would bring "substantial benefits" to the region "if fully implemented."