As revealed by the Church Committee - one of the intelligence-related enquiries that sprung up like mushrooms after Watergate, the CIA actively plotted to assassinate Lumumba.

For example, at the time of Lumumba's death, CIA toxin expert Sidney Gottlieb was in Africa, equipped with deadly bacteria, and hoping to use these to bring the politician's life to a premature end (see the Church Committee's Alleged Assassination Plots Involving Foreign Leaders, pp. 20-21.)

As with Fidel Castro, it's not unlikely that the CIA were running more than one simultaneous operation with the same end in view. Lumumba had certainly caused some concern at the Agency. The political situation was complicated. Belgium had encouraged the secession of the Congo's wealthiest province, Katanga, virtually owned by the Belgian company Union Miniere du Haut Katanga. Katanga was a rich prize, and Lumumba sought to regain it for his country. After his appeal for aid from the US was rebuffed with the implausible suggestion that he go instead to the UN, he indicated that he would be happy to accept help from any nation willing to give it. Russia, unfortunately for Lumumba, proved willing.

By mid 1960, around 10,000 of the UN's strangely ineffective peacekeeping troops were in the country. As direct Russian help started to be made available, the US view of Lumumba - already an annoyance - began to darken. Rumours circulated that Lumumba was a dope-smoking witchcraft practitioner with loose sexual morals. According to the Church committee, Allen Dulles "said that in Lumumba we were faced with a person who was a Castro or worse."

On August 25, 1960, Dulles cabled CIA station chief in Leopoldville, Lawrence Devlin:

In high quarters here it is the clear-cut conclusion that if Lumumba continues to hold high office, the inevitable result will at best be chaos and at worst pave the way to Communist takeover of the Congo with disastrous consequences for the prestige of the UN and the interests of the Free World generally. Consequently we conclude that his removal must be an urgent and prime objective and that under existing conditions this should be a high priority of our covert action.
As usual with 'official' communications authorising illegal acts, such as murder, the wording is inexact and open to interpretation, as required by Eisenhower's doctrine of plausible denial. Such communications were usually explicated by more sanguine, unrecorded, instructions on a 'back channel'. The minutes of the Special Group (Eisenhower's covert action committee) use somewhat plainer language, reporting Dulles as saying: "Lumumba was not yet disposed of and remained a grave danger as long as he was not disposed of" and noting the conclusion "planning for the Congo would not rule out 'consideration' of any particular kind of activity which might contribute to getting rid of Lumumba" (Special Group minutes, August 25, 1960)

The Church committee ultimately concluded that it was not a CIA assassin who brought Lumumba's political career to a sudden end - in fact they reached the fairly preposterous conclusion that though the CIA had had people - experts in the field - working hard to assassinate about five or six political leaders whose policies they found distasteful, it was always some other guys who got there first. Darn!

Information from John Ranelagh's quasi-official apologia The Agency - the rise and decline of the CIA