The Prophet (peace and blessings be upon him) said, “Islam is built upon five pillars: testifying that there is no true god except Allah and that Muhammad is the Messenger of Allah, performing Prayer, paying the Zakah, making the pilgrimage to the Sacred House (Hajj), and fasting the month of Ramadan.” (Al-Bukhari)
Therefore, it should be clear that Hajj is obligatory on one who is financially and physically capable to perform it. If one is not financially able to perform Hajj but he can only afford for `Umrah, then he is not required to perform Hajj until he attains the financial capability to perform it. Once he has the means to perform Hajj, he is required to perform it immediately.