WASHINGTON-Two U.S. senators are holding up the Bush administration's nominee for ambassador to Macedonia, which has been engaged in a dispute with Greece over its name.

The senators have not been identified, but aides on the Senate Foreign Relations Committee identified them as Republican Sen. Olympia Snowe and Democratic Sen. Robert Menendez. Aides from the committee spoke on condition of anonymity because they were not authorized to speak to the press about the nomination.

The two lawmakers' offices refused comment, and it is unclear whether they intend to block the nomination of Philip Reeker or simply to delay it.

However, Snowe's office provided The Associated Press with a letter to Secretary of State Condoleezza Rice, dated July 10, that criticizes Bush administration policy on the question.

The hold on the nomination comes at a time that Greece has been complicating Macedonia's diplomatic relations to exert pressure over the name dispute, an issue that aides say is behind the hold up of Reeker's nomination.

A United Nations envoy has been brokering talks aimed at reaching a name both countries can accept.

Greece argues the name Macedonia implies expansionist claims on its northern province of the same name, which the country of Macedonia rejects. Greece has complained that the Macedonian government has been responsible for hostile propaganda, including maps used in textbooks that show parts of Greece within Macedonian borders.

Snowe's letter criticizes the Bush administration for its 2004 decision to recognize Macedonia as "the Republic of Macedonia." It asks Rice to confirm that the administration is encouraging Macedonia to stop "hostile activities or propaganda."

Athens has vowed to prevent its neighbor from joining NATO or the European Union until the issue is resolved and indeed already blocked Macedonia's invitation to NATO this year. United Nations-brokered talks aimed at resolving the dispute have been deadlocked. The country is listed at the United Nations under the provisional name of Former Yugoslav Republic of Macedonia, or FYROM.

Senators can block nominations anonymously. A congressional aide said that when the nomination came up in the Foreign Relations Committee, there were a spate of phone calls from Greek-American groups, who were concerned about recent violence in Macedonia and asked lawmakers to force Reeker to answer further questions before he could be confirmed.

Macedonia has experienced a series of violent attacks among ethnic Albanians. The ethnic minority's two main parties have been locked in a bitter rivalry that led to violent disruptions to the country's parliamentary election last month and forced many areas to hold reruns twice, on June 15 and 29.

Reeker, a career diplomat, was recently spokesman in the U.S. Embassy in Baghdad. The State Department would not comment on the Senate's consideration of the nomination.