The US State Department on Wednesday called on Egypt to fulfill its obligations under its peace treaty with Israel and deal strongly with security threats in the Sinai.It also asked that Egypt make sure that "lines of communication stay open."In answer to a question about reports that Egypt would move tanks and aircraft into the Sinai for the first time since 1973, US State Department spokesperson Victoria Nuland told reporters that "as the Egyptians work hard now to defeat terror and turn back other security threats in the Sinai, we’ve been supportive of those efforts. We have encouraged them in those efforts, not only to enhance security in Egypt but also to enhance security for neighbors, security in the region."Nuland also said that the US is speaking to the Israelis. "They want to see security in Sinai enhanced, and they want to see it enhanced in a manner that is also respectful of treaty obligations," Nuland said.The movement of military hardware into the Sinai comes after a deadly attack earlier this month on Egyptian border guards that left 16 dead. Part of the assault included an attempt to breach the border with Israel. Israel reportedly had warned Egypt about the attack before it happened.Following the attack, Israel agreed to the movement of additional Egyptian troops into the region to control the terrorists.Under the 1979 peace treaty between Egypt and Israel, Israel agreed to withdraw its troops and citizens from the Sinai and return it to Egypt in return for normalized relations and a restriction on the number of Egyptian troops allowed to enter the Sinai, particularly near the border with Israel.Israel has called on Egypt to control the terrorists in the Sinai.