The position of the new Honduran government is that if Zelaya comes back to Honduras he will be arrested and charged with several crimes. They have also said that only an invasion could reinstate Zelaya as president. Unless the Honduran government changes its tune and position it does not seem possible that diplomacy could bring about Zelaya's return.
The head of the OAS Jose Insulza is going to Honduras on Friday to insist on the restoration of Zelaya. Insulza claims that sanctions are likely in Honduras since the Honduran government will probably not comply with the OAS demands. The deadline for Honduras to comply with the demand to reinstate Zelaya is Saturday.
The U.S. seems to be leaving negotiations to the OAS rather than taking a lead role itself. The US invaded Panama to seize Noriega and take him to the US to be tried on drug charges. The US also invaded Grenada as they did not like what was going on there in the Marxist oriented government. However, I doubt that the US will invade Honduras to reinstate Zelaya! At least the U.S. this time has not sided with or supported the coup leaders. Here is a recent article on Insulza's visit:
http://news.yahoo.com/s/ap/20090703/ap_o