Ethnic Albanian guerrillas known as the National Liberation Army (NLA) have called for a new Macedonian constitution, better rights for Albanians, and international mediation.
Mr Cook told BBC Radio 4's Today programme that he had discussed the situation in the Macedonian border town of Tetovo with US Secretary of State Colin Powell and several European foreign ministers.
Ethnic Albanian guerrillas known as the National Liberation Army (NLA) have called for a new Macedonian constitution, better rights for Albanians, and international mediation.
The Macedonian Government has given the rebels until midnight to surrender or withdraw from Macedonian territory, otherwise it says it will use all available means against them.
Mr Cook said: "We all agreed that K-For [Nato-led peacekeeping force] must show a robust and rapid response by stepping up its patrols on the border, on the ground and in the air."
K-For should also step up efforts to share intelligence information with the Macedonian army "to make sure that we together defeat the terrorists' attempts to move across the border," Mr Cook added.
Legitimate demands
The conflict in the former Yugoslav republic has escalated in recent weeks leaving up to 10,000 people displaced from their homes.
Mr Cook said the UK wanted to work with the Macedonian government to defeat the rebels.
But as well as a "robust" military response, he said the Macedonian Government needed to respond to "legitimate political demands of the Albanian community".
Mr Cook dismissed the suggestion that K-For should take direct action against the rebels in Macedonia.
But he said the Macedonian Government was a democratic authority, "not a repressive regime" and included representatives of an Albanian party.
Ethnic Albanians make up a quarter of Macedonia's population.
Mr Cook said Britain had shown its support in the past by putting £500,000 into an Albanian University in Tetovo.